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SYSK 391: Entities as a data contract

  • Article

There may be instances when using data transfer objects (DTO) is appropriate. For example, if you need to control the serialization details, such as which members to serialize and which not to serialize, and if you need to change the names of the serialized members, or do data contract mapping based on service version, or you want to suppress custom logic in entities created via partial classes, etc.  If you choose to use DTOs, consider using generator classes, e.g. EntitiesToDTOs - Entity Framework DTO Generator available at http://visualstudiogallery.msdn.microsoft.com/655aa6d4-4461-42ea-aeec-64cdb1313de7, DTO from Entity Framework Class at http://www.codeproject.com/Tips/739566/DTO-from-Entity-Framework-class or others.

On my current project, however, there were no requirements that would direct us the DTO route, and since Entity Framework automatically creates a data contract for entities in your EDMX model, I was hoping to use the T4 generated classes as is.  However, there were two problems:

  1. Using T4 generated entities as a contract in an asmx service would result in an error due to ICollection<T> used for 1->M navigation properties (e.g. Person -> Phones)
  2. Entity Framework uses dynamic proxies for change tracking and lazy loading.  When returning results of an operation to the caller, serialization of navigation properties that are not loaded will trigger lazy loading resulting in a runtime exception because the DbContext is already disposed. 

You can turn off generation of the proxies by setting dbContext.Configuration.ProxyCreationEnabled to False.  However, you will lose the lazy loading functionality and will have to eagerly or explicitly load related objects.   You will also lose change tracking which may be acceptable in a service Get operation because change tracking only works on entities attached to a context, and that’s not the case once the data is returned to the caller of the service.

To deal with the aforementioned issues, you can modify the T4 template as demonstrated below.  Most of the needed work will be accomplished by the code-generated classes.  The only thing required to take advantage of this functionality is to call AsSerializable() upon returning results from your service, e.g.:

public Person GetData(int id) {     Person result = null;      using (var ctx = new ModelEntities())     {         result = (from e in ctx.Person.Include("Phones") where e.PersonID == id select e).FirstOrDefault();     }      return result .AsSerializable(); } 

 

Model.tt file
Changes highlighted

<#@ template language="C#" debug="false" hostspecific="true"#>
<#@ include file="EF6.Utility.CS.ttinclude"#><#@
 output extension=".cs"#><#

const string inputFile = @"..\DataAccess\Model1.edmx";
var textTransform = DynamicTextTransformation.Create(this);
var code = new CodeGenerationTools(this);
var ef = new MetadataTools(this);
var typeMapper = new TypeMapper(code, ef, textTransform.Errors);
var fileManager = EntityFrameworkTemplateFileManager.Create(this);
var itemCollection = new EdmMetadataLoader(textTransform.Host, textTransform.Errors).CreateEdmItemCollection(inputFile);
var codeStringGenerator = new CodeStringGenerator(code, typeMapper, ef);

if (!typeMapper.VerifyCaseInsensitiveTypeUniqueness(typeMapper.GetAllGlobalItems(itemCollection), inputFile))
{
    return string.Empty;
}

WriteHeader(codeStringGenerator, fileManager);

fileManager.StartNewFile("Serializable.cs");
BeginNamespace(code);
SerializableObject();
EndNamespace(code);

foreach (var entity in typeMapper.GetItemsToGenerate<EntityType>(itemCollection))
{
    fileManager.StartNewFile(entity.Name + ".cs");
    BeginNamespace(code);
#>
<#=codeStringGenerator.UsingDirectives(inHeader: false)#>
<#=codeStringGenerator.EntityClassOpening(entity)#>
{
<#
    var propertiesWithDefaultValues = typeMapper.GetPropertiesWithDefaultValues(entity);
    var collectionNavigationProperties = typeMapper.GetCollectionNavigationProperties(entity);
    var complexProperties = typeMapper.GetComplexProperties(entity);

    //if (propertiesWithDefaultValues.Any() || collectionNavigationProperties.Any() || complexProperties.Any())
    {
#>
    public <#=code.Escape(entity)#>()
    {
<#
        foreach (var edmProperty in propertiesWithDefaultValues)
        {
#>
        this.<#=code.Escape(edmProperty)#> = <#=typeMapper.CreateLiteral(edmProperty.DefaultValue)#>;
<#
        }

        foreach (var navigationProperty in collectionNavigationProperties)
        {
#>
  this.<#=code.Escape(navigationProperty)#> = new List<<#=typeMapper.GetTypeName(navigationProperty.ToEndMember.GetEntityType())#>>();
<#
        }

        foreach (var complexProperty in complexProperties)
        {
#>
        this.<#=code.Escape(complexProperty)#> = new <#=typeMapper.GetTypeName(complexProperty.TypeUsage)#>();
<#
        }
#>
    }

 private <#=code.Escape(entity)#>(<#=code.Escape(entity)#> obj) : base(obj, null) { }
 private <#=code.Escape(entity)#>(<#=code.Escape(entity)#> obj, Dictionary<Type, object> createdTypes) : base(obj, createdTypes) { }
<# 

    }

 

    var simpleProperties = typeMapper.GetSimpleProperties(entity);
    if (simpleProperties.Any())
    {
        foreach (var edmProperty in simpleProperties)
        {
#>
    <#=codeStringGenerator.Property(edmProperty)#>
<#
        }
    }

    if (complexProperties.Any())
    {
#>

<#
        foreach(var complexProperty in complexProperties)
        {
#>
    <#=codeStringGenerator.Property(complexProperty)#>
<#
        }
    }

    var navigationProperties = typeMapper.GetNavigationProperties(entity);
    if (navigationProperties.Any())
    {
#>

<#
        foreach (var navigationProperty in navigationProperties)
        {
#>
    <#=codeStringGenerator.NavigationProperty(navigationProperty)#>
<#
        }
    }
#>
}
<#
    EndNamespace(code);
}

foreach (var complex in typeMapper.GetItemsToGenerate<ComplexType>(itemCollection))
{
    fileManager.StartNewFile(complex.Name + ".cs");
    BeginNamespace(code);
#>
<#=codeStringGenerator.UsingDirectives(inHeader: false, includeCollections: false)#>
<#=Accessibility.ForType(complex)#> partial class <#=code.Escape(complex)#>  
{
<#
    var complexProperties = typeMapper.GetComplexProperties(complex);
    var propertiesWithDefaultValues = typeMapper.GetPropertiesWithDefaultValues(complex);

    if (propertiesWithDefaultValues.Any() || complexProperties.Any())
    {
#>
    public <#=code.Escape(complex)#>()
    {
<#
        foreach (var edmProperty in propertiesWithDefaultValues)
        {
#>
        this.<#=code.Escape(edmProperty)#> = <#=typeMapper.CreateLiteral(edmProperty.DefaultValue)#>;
<#
        }

        foreach (var complexProperty in complexProperties)
        {
#>
        this.<#=code.Escape(complexProperty)#> = new <#=typeMapper.GetTypeName(complexProperty.TypeUsage)#>();
<#
        }
#>
    }

<#
    }

    var simpleProperties = typeMapper.GetSimpleProperties(complex);
    if (simpleProperties.Any())
    {
        foreach(var edmProperty in simpleProperties)
        {
#>
    <#=codeStringGenerator.Property(edmProperty)#>
<#
        }
    }

    if (complexProperties.Any())
    {
#>

<#
        foreach(var edmProperty in complexProperties)
        {
#>
    <#=codeStringGenerator.Property(edmProperty)#>
<#
        }
    }
#>
}
<#
    EndNamespace(code);
}

foreach (var enumType in typeMapper.GetEnumItemsToGenerate(itemCollection))
{
    fileManager.StartNewFile(enumType.Name + ".cs");
    BeginNamespace(code);
#>
<#=codeStringGenerator.UsingDirectives(inHeader: false, includeCollections: false)#>
<#
    if (typeMapper.EnumIsFlags(enumType))
    {
#>
[Flags]
<#
    }
#>
<#=codeStringGenerator.EnumOpening(enumType)#>
{
<#
    var foundOne = false;
   
    foreach (MetadataItem member in typeMapper.GetEnumMembers(enumType))
    {
        foundOne = true;
#>
    <#=code.Escape(typeMapper.GetEnumMemberName(member))#> = <#=typeMapper.GetEnumMemberValue(member)#>,
<#
    }

    if (foundOne)
    {
        this.GenerationEnvironment.Remove(this.GenerationEnvironment.Length - 3, 1);
    }
#>
}
<#
    EndNamespace(code);
}

fileManager.Process();

#>
<#+

public void WriteHeader(CodeStringGenerator codeStringGenerator, EntityFrameworkTemplateFileManager fileManager)
{
    fileManager.StartHeader();
#>
//------------------------------------------------------------------------------
// <auto-generated>
// <#=CodeGenerationTools.GetResourceString("Template_GeneratedCodeCommentLine1")#>
//
// <#=CodeGenerationTools.GetResourceString("Template_GeneratedCodeCommentLine2")#>
// <#=CodeGenerationTools.GetResourceString("Template_GeneratedCodeCommentLine3")#>
// </auto-generated>
//------------------------------------------------------------------------------
<#=codeStringGenerator.UsingDirectives(inHeader: true)#>
<#+
    fileManager.EndBlock();
}

public void BeginNamespace(CodeGenerationTools code)
{
    var codeNamespace = code.VsNamespaceSuggestion();
    if (!String.IsNullOrEmpty(codeNamespace))
    {
#>
namespace <#=code.EscapeNamespace(codeNamespace)#>
{
<#+
        PushIndent(" ");
    }
}

public void EndNamespace(CodeGenerationTools code)
{
    if (!String.IsNullOrEmpty(code.VsNamespaceSuggestion()))
    {
        PopIndent();
#>
}
<#+
    }
}

public void SerializableObject()
{
#>
using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using System.Runtime.Serialization;

[DataContract]
public abstract class SerializableObject<T> where T : class
{
    [NonSerialized]
    private Dictionary<Type, object> CreatedTypes = null;

    [DataMember]
    public T OriginalValues { get; private set; }

    public T AsSerializable()
    {        
  T origValues = CreateInstance(typeof(T), new object[] { this }) as T;
   (origValues as SerializableObject<T>).OriginalValues = null;

  T result = CreateInstance(typeof(T), new object[] { this }) as T;
   (result as SerializableObject<T>).OriginalValues = origValues;

  return result;
    }

    public SerializableObject() { }

    protected SerializableObject(T o, Dictionary<Type, object> createdTypes)
    {
        this.CreatedTypes = createdTypes == null ? new Dictionary<Type, object>() : createdTypes;

        if (createdTypes == null)
            this.CreatedTypes.Add(this.GetType(), this);

        foreach (var f in this.GetType().GetFields(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance))
        {
            System.Diagnostics.Debug.WriteLine(f.Name);
            object fv = f.GetValue(o);
            if (fv != null && fv.GetType().IsGenericType)
            {
                Type t = fv.GetType().GetGenericTypeDefinition();
                Type fieldType = t.MakeGenericType(fv.GetType().GenericTypeArguments);
                IList items = null;

                if (fv is IEnumerable)
                {
                    Type itemType = null;
                    Type itemsType = typeof(List<>).GetGenericTypeDefinition();

                    foreach (var i in fv as IEnumerable)
                    {
                        if (itemType == null)
                        {
                            // TODO: Remove reliance on the string EntityProxyModule
                            if (i.GetType().Module.ScopeName == "EntityProxyModule")
                                itemType = i.GetType().BaseType;
                            else
                                itemType = i.GetType();

                            items = Activator.CreateInstance(itemsType.MakeGenericType(itemType)) as IList;
                        }

                        object item = CreateInstance(itemType, new object[] { i });
                        items.Add(item);
                    }

                    dynamic v = CreateInstance(fieldType, new object[] { items });
                    f.SetValue(this, v);

                }
                else
                {
                    f.SetValue(this, CreateInstance(fieldType, new object[] { fv }));
                }
            }
            else
            {
                if (fv != null)
                {
                    // TODO: Remove reliance on the string EntityProxyModule
                    if (fv.GetType().Module.ScopeName == "EntityProxyModule")
                    {
                        fv = CreateInstance(fv.GetType().BaseType, new object[] { fv }, true);
                    }
                }
                f.SetValue(this, fv);
            }
        }
    }

    private object CreateInstance(Type t, object[] args, bool cache = false)
    {
        object result = null;

        if (this.CreatedTypes != null && this.CreatedTypes.ContainsKey(t))
        {
            // Return null to avoid circular references leading to runtime exceptions like
            /*
                An exception of type 'Microsoft.CSharp.RuntimeBinder.RuntimeBinderException' occurred in System.Core.dll but was not handled in user code
                Additional information: The best overloaded method match for 'System.Collections.Generic.HashSet<ClassLibrary2.Phone>.Add(ClassLibrary2.Phone)' has some invalid arguments

                    at CallSite.Target(Closure , CallSite , Object , Object )
                    at System.Dynamic.UpdateDelegates.UpdateAndExecuteVoid2[T0,T1](CallSite site, T0 arg0, T1 arg1)
                    at ClassLibrary2.SerializableObject`1..ctor(T o, Dictionary`2 createdTypes) in c:\Temp\xx\ClassLibrary2\Class1.cs:line 60
                    at ClassLibrary2.SerializableObject`1..ctor(T o) in c:\Temp\xx\ClassLibrary2\Class1.cs:line 20
                    at ClassLibrary2.Employee..ctor(Employee e) in c:\Temp\xx\ClassLibrary2\Class1.cs:line 122
                    at WcfServiceLibrary1.Service1.GetData(Int32 value) in c:\Temp\xx\WcfServiceLibrary1\Service1.cs:line 24
                    at SyncInvokeGetData(Object , Object[] , Object[] )
                    at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]& outputs)
                    at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc)

            */
            // result = this.CreatedTypes[t];
            result = null;
        }
        else
        {
            Type gt = typeof(SerializableObject<>).GetGenericTypeDefinition();

            if (t.IsSubclassOf(gt.MakeGenericType(t)))
            {
                List<object> newArgs = new List<object>();
                newArgs.AddRange(args);
                newArgs.Add(this.CreatedTypes);

                var ctor = t.GetConstructor(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance, null,
                    new Type[] { t, typeof(Dictionary<Type, object>) }, null);
                System.Diagnostics.Debug.Assert(ctor != null);
                result = ctor.Invoke(newArgs.ToArray());
            }
            else
            {
                if (args[0] == null)
                    result = Activator.CreateInstance(t);
                else
                    result = Activator.CreateInstance(t, args);
            }

            if (cache)
                this.CreatedTypes.Add(t, result);
        }

        return result;
  }
}
  <#+

}

public const string TemplateId = "CSharp_DbContext_Types_EF6";

public class CodeStringGenerator
{
    private readonly CodeGenerationTools _code;
    private readonly TypeMapper _typeMapper;
    private readonly MetadataTools _ef;

    public CodeStringGenerator(CodeGenerationTools code, TypeMapper typeMapper, MetadataTools ef)
    {
        ArgumentNotNull(code, "code");
        ArgumentNotNull(typeMapper, "typeMapper");
        ArgumentNotNull(ef, "ef");

        _code = code;
        _typeMapper = typeMapper;
        _ef = ef;
    }

    public string Property(EdmProperty edmProperty)
    {
        return string.Format(
            CultureInfo.InvariantCulture,
            "{0} {1} {2} {{ {3}get; {4}set; }}",
            Accessibility.ForProperty(edmProperty),
            _typeMapper.GetTypeName(edmProperty.TypeUsage),
            _code.Escape(edmProperty),
            _code.SpaceAfter(Accessibility.ForGetter(edmProperty)),
            _code.SpaceAfter(Accessibility.ForSetter(edmProperty)));
    }

    public string NavigationProperty(NavigationProperty navProp)
    {
        var endType = _typeMapper.GetTypeName(navProp.ToEndMember.GetEntityType());
        return string.Format(
            CultureInfo.InvariantCulture,
            "{0} {1} {2} {{ {3}get; {4}set; }}",
            AccessibilityAndVirtual(Accessibility.ForNavigationProperty(navProp)),
   navProp.ToEndMember.RelationshipMultiplicity == RelationshipMultiplicity.Many ? ("List<" + endType + ">") : endType,
            _code.Escape(navProp),
            _code.SpaceAfter(Accessibility.ForGetter(navProp)),
            _code.SpaceAfter(Accessibility.ForSetter(navProp)));
    }
   
    public string AccessibilityAndVirtual(string accessibility)
    {
        return accessibility + (accessibility != "private" ? " virtual" : "");
    }
   
    public string EntityClassOpening(EntityType entity)
    {
  var baseType = entity.BaseType != null ? _typeMapper.GetTypeName(entity.BaseType)
    : "SerializableObject<" + _code.Escape(entity) + ">";

        return string.Format(
            CultureInfo.InvariantCulture,
            "{0} {1}partial class {2}{3}",
            Accessibility.ForType(entity),
            _code.SpaceAfter(_code.AbstractOption(entity)),
            _code.Escape(entity),
            _code.StringBefore(" : ", baseType ));
    }
   
    public string EnumOpening(SimpleType enumType)
    {
        return string.Format(
            CultureInfo.InvariantCulture,
            "{0} enum {1} : {2}",
            Accessibility.ForType(enumType),
            _code.Escape(enumType),
            _code.Escape(_typeMapper.UnderlyingClrType(enumType)));
        }
   
    public void WriteFunctionParameters(EdmFunction edmFunction, Action<string, string, string, string> writeParameter)
    {
        var parameters = FunctionImportParameter.Create(edmFunction.Parameters, _code, _ef);
        foreach (var parameter in parameters.Where(p => p.NeedsLocalVariable))
        {
            var isNotNull = parameter.IsNullableOfT ? parameter.FunctionParameterName + ".HasValue" : parameter.FunctionParameterName + " != null";
            var notNullInit = "new ObjectParameter(\"" + parameter.EsqlParameterName + "\", " + parameter.FunctionParameterName + ")";
            var nullInit = "new ObjectParameter(\"" + parameter.EsqlParameterName + "\", typeof(" + TypeMapper.FixNamespaces(parameter.RawClrTypeName) + "))";
            writeParameter(parameter.LocalVariableName, isNotNull, notNullInit, nullInit);
        }
    }
   
    public string ComposableFunctionMethod(EdmFunction edmFunction, string modelNamespace)
    {
        var parameters = _typeMapper.GetParameters(edmFunction);
       
        return string.Format(
            CultureInfo.InvariantCulture,
            "{0} IQueryable<{1}> {2}({3})",
            AccessibilityAndVirtual(Accessibility.ForMethod(edmFunction)),
            _typeMapper.GetTypeName(_typeMapper.GetReturnType(edmFunction), modelNamespace),
            _code.Escape(edmFunction),
            string.Join(", ", parameters.Select(p => TypeMapper.FixNamespaces(p.FunctionParameterType) + " " + p.FunctionParameterName).ToArray()));
    }
   
    public string ComposableCreateQuery(EdmFunction edmFunction, string modelNamespace)
    {
        var parameters = _typeMapper.GetParameters(edmFunction);
       
        return string.Format(
            CultureInfo.InvariantCulture,
            "return ((IObjectContextAdapter)this).ObjectContext.CreateQuery<{0}>(\"[{1}].[{2}]({3})\"{4});",
            _typeMapper.GetTypeName(_typeMapper.GetReturnType(edmFunction), modelNamespace),
            edmFunction.NamespaceName,
            edmFunction.Name,
            string.Join(", ", parameters.Select(p => "@" + p.EsqlParameterName).ToArray()),
            _code.StringBefore(", ", string.Join(", ", parameters.Select(p => p.ExecuteParameterName).ToArray())));
    }
   
    public string FunctionMethod(EdmFunction edmFunction, string modelNamespace, bool includeMergeOption)
    {
        var parameters = _typeMapper.GetParameters(edmFunction);
        var returnType = _typeMapper.GetReturnType(edmFunction);

        var paramList = String.Join(", ", parameters.Select(p => TypeMapper.FixNamespaces(p.FunctionParameterType) + " " + p.FunctionParameterName).ToArray());
        if (includeMergeOption)
        {
            paramList = _code.StringAfter(paramList, ", ") + "MergeOption mergeOption";
        }

        return string.Format(
            CultureInfo.InvariantCulture,
            "{0} {1} {2}({3})",
            AccessibilityAndVirtual(Accessibility.ForMethod(edmFunction)),
            returnType == null ? "int" : "ObjectResult<" + _typeMapper.GetTypeName(returnType, modelNamespace) + ">",
            _code.Escape(edmFunction),
            paramList);
    }
   
    public string ExecuteFunction(EdmFunction edmFunction, string modelNamespace, bool includeMergeOption)
    {
        var parameters = _typeMapper.GetParameters(edmFunction);
        var returnType = _typeMapper.GetReturnType(edmFunction);

        var callParams = _code.StringBefore(", ", String.Join(", ", parameters.Select(p => p.ExecuteParameterName).ToArray()));
        if (includeMergeOption)
        {
            callParams = ", mergeOption" + callParams;
        }
       
        return string.Format(
            CultureInfo.InvariantCulture,
            "return ((IObjectContextAdapter)this).ObjectContext.ExecuteFunction{0}(\"{1}\"{2});",
            returnType == null ? "" : "<" + _typeMapper.GetTypeName(returnType, modelNamespace) + ">",
            edmFunction.Name,
            callParams);
    }
   
    public string DbSet(EntitySet entitySet)
    {
        return string.Format(
            CultureInfo.InvariantCulture,
            "{0} virtual DbSet<{1}> {2} {{ get; set; }}",
            Accessibility.ForReadOnlyProperty(entitySet),
            _typeMapper.GetTypeName(entitySet.ElementType),
            _code.Escape(entitySet));
    }

    public string UsingDirectives(bool inHeader, bool includeCollections = true)
    {
        return inHeader == string.IsNullOrEmpty(_code.VsNamespaceSuggestion())
            ? string.Format(
                CultureInfo.InvariantCulture,
                "{0}using System;{1}" +
                "{2}",
                inHeader ? Environment.NewLine : "",
                includeCollections ? (Environment.NewLine + "using System.Collections.Generic;") : "",
                inHeader ? "" : Environment.NewLine)
            : "";
    } 

}

public class TypeMapper
{
    private const string ExternalTypeNameAttributeName = @"http://schemas.microsoft.com/ado/2006/04/codegeneration:ExternalTypeName";

    private readonly System.Collections.IList _errors;
    private readonly CodeGenerationTools _code;
    private readonly MetadataTools _ef;

    public TypeMapper(CodeGenerationTools code, MetadataTools ef, System.Collections.IList errors)
    {
        ArgumentNotNull(code, "code");
        ArgumentNotNull(ef, "ef");
        ArgumentNotNull(errors, "errors");

        _code = code;
        _ef = ef;
        _errors = errors;
    }

    public static string FixNamespaces(string typeName)
    {
        return typeName.Replace("System.Data.Spatial.", "System.Data.Entity.Spatial.");
    }

    public string GetTypeName(TypeUsage typeUsage)
    {
        return typeUsage == null ? null : GetTypeName(typeUsage.EdmType, _ef.IsNullable(typeUsage), modelNamespace: null);
    }

    public string GetTypeName(EdmType edmType)
    {
        return GetTypeName(edmType, isNullable: null, modelNamespace: null);
    }

    public string GetTypeName(TypeUsage typeUsage, string modelNamespace)
    {
        return typeUsage == null ? null : GetTypeName(typeUsage.EdmType, _ef.IsNullable(typeUsage), modelNamespace);
    }

    public string GetTypeName(EdmType edmType, string modelNamespace)
    {
        return GetTypeName(edmType, isNullable: null, modelNamespace: modelNamespace);
    }

    public string GetTypeName(EdmType edmType, bool? isNullable, string modelNamespace)
    {
        if (edmType == null)
        {
            return null;
        }

        var collectionType = edmType as CollectionType;
        if (collectionType != null)
        {
            return String.Format(CultureInfo.InvariantCulture, "List<{0}>", GetTypeName(collectionType.TypeUsage, modelNamespace));
        }

        var typeName = _code.Escape(edmType.MetadataProperties
                                .Where(p => p.Name == ExternalTypeNameAttributeName)
                                .Select(p => (string)p.Value)
                                .FirstOrDefault())
            ?? (modelNamespace != null && edmType.NamespaceName != modelNamespace ?
                _code.CreateFullName(_code.EscapeNamespace(edmType.NamespaceName), _code.Escape(edmType)) :
                _code.Escape(edmType));

        if (edmType is StructuralType)
        {
            return typeName;
        }

        if (edmType is SimpleType)
        {
            var clrType = UnderlyingClrType(edmType);
            if (!IsEnumType(edmType))
            {
                typeName = _code.Escape(clrType);
            }

            typeName = FixNamespaces(typeName);

            return clrType.IsValueType && isNullable == true ?
                String.Format(CultureInfo.InvariantCulture, "Nullable<{0}>", typeName) :
                typeName;
        }

        throw new ArgumentException("edmType");
    }
   
    public Type UnderlyingClrType(EdmType edmType)
    {
        ArgumentNotNull(edmType, "edmType");

        var primitiveType = edmType as PrimitiveType;
        if (primitiveType != null)
        {
            return primitiveType.ClrEquivalentType;
        }

        if (IsEnumType(edmType))
        {
            return GetEnumUnderlyingType(edmType).ClrEquivalentType;
        }

        return typeof(object);
    }
   
    public object GetEnumMemberValue(MetadataItem enumMember)
    {
        ArgumentNotNull(enumMember, "enumMember");
       
        var valueProperty = enumMember.GetType().GetProperty("Value");
        return valueProperty == null ? null : valueProperty.GetValue(enumMember, null);
    }
   
    public string GetEnumMemberName(MetadataItem enumMember)
    {
        ArgumentNotNull(enumMember, "enumMember");
       
        var nameProperty = enumMember.GetType().GetProperty("Name");
        return nameProperty == null ? null : (string)nameProperty.GetValue(enumMember, null);
    }

    public System.Collections.IEnumerable GetEnumMembers(EdmType enumType)
    {
        ArgumentNotNull(enumType, "enumType");

        var membersProperty = enumType.GetType().GetProperty("Members");
        return membersProperty != null
            ? (System.Collections.IEnumerable)membersProperty.GetValue(enumType, null)
            : Enumerable.Empty<MetadataItem>();
    }
   
    public bool EnumIsFlags(EdmType enumType)
    {
        ArgumentNotNull(enumType, "enumType");
       
        var isFlagsProperty = enumType.GetType().GetProperty("IsFlags");
        return isFlagsProperty != null && (bool)isFlagsProperty.GetValue(enumType, null);
    }

    public bool IsEnumType(GlobalItem edmType)
    {
        ArgumentNotNull(edmType, "edmType");

        return edmType.GetType().Name == "EnumType";
    }

    public PrimitiveType GetEnumUnderlyingType(EdmType enumType)
    {
        ArgumentNotNull(enumType, "enumType");

        return (PrimitiveType)enumType.GetType().GetProperty("UnderlyingType").GetValue(enumType, null);
    }

    public string CreateLiteral(object value)
    {
        if (value == null || value.GetType() != typeof(TimeSpan))
        {
            return _code.CreateLiteral(value);
        }

        return string.Format(CultureInfo.InvariantCulture, "new TimeSpan({0})", ((TimeSpan)value).Ticks);
    }
   
    public bool VerifyCaseInsensitiveTypeUniqueness(IEnumerable<string> types, string sourceFile)
    {
        ArgumentNotNull(types, "types");
        ArgumentNotNull(sourceFile, "sourceFile");
       
        var hash = new HashSet<string>(StringComparer.InvariantCultureIgnoreCase);
        if (types.Any(item => !hash.Add(item)))
        {
            _errors.Add(
                new CompilerError(sourceFile, -1, -1, "6023",
                    String.Format(CultureInfo.CurrentCulture, CodeGenerationTools.GetResourceString("Template_CaseInsensitiveTypeConflict"))));
            return false;
        }
        return true;
    }
   
    public IEnumerable<SimpleType> GetEnumItemsToGenerate(IEnumerable<GlobalItem> itemCollection)
    {
        return GetItemsToGenerate<SimpleType>(itemCollection)
            .Where(e => IsEnumType(e));
    }
   
    public IEnumerable<T> GetItemsToGenerate<T>(IEnumerable<GlobalItem> itemCollection) where T: EdmType
    {
        return itemCollection
            .OfType<T>()
            .Where(i => !i.MetadataProperties.Any(p => p.Name == ExternalTypeNameAttributeName))
            .OrderBy(i => i.Name);
    }

    public IEnumerable<string> GetAllGlobalItems(IEnumerable<GlobalItem> itemCollection)
    {
        return itemCollection
            .Where(i => i is EntityType || i is ComplexType || i is EntityContainer || IsEnumType(i))
            .Select(g => GetGlobalItemName(g));
    }

    public string GetGlobalItemName(GlobalItem item)
    {
        if (item is EdmType)
        {
            return ((EdmType)item).Name;
        }
        else
        {
            return ((EntityContainer)item).Name;
        }
    }

    public IEnumerable<EdmProperty> GetSimpleProperties(EntityType type)
    {
        return type.Properties.Where(p => p.TypeUsage.EdmType is SimpleType && p.DeclaringType == type);
    }
   
    public IEnumerable<EdmProperty> GetSimpleProperties(ComplexType type)
    {
        return type.Properties.Where(p => p.TypeUsage.EdmType is SimpleType && p.DeclaringType == type);
    }
   
    public IEnumerable<EdmProperty> GetComplexProperties(EntityType type)
    {
        return type.Properties.Where(p => p.TypeUsage.EdmType is ComplexType && p.DeclaringType == type);
    }
   
    public IEnumerable<EdmProperty> GetComplexProperties(ComplexType type)
    {
        return type.Properties.Where(p => p.TypeUsage.EdmType is ComplexType && p.DeclaringType == type);
    }

    public IEnumerable<EdmProperty> GetPropertiesWithDefaultValues(EntityType type)
    {
        return type.Properties.Where(p => p.TypeUsage.EdmType is SimpleType && p.DeclaringType == type && p.DefaultValue != null);
    }
   
    public IEnumerable<EdmProperty> GetPropertiesWithDefaultValues(ComplexType type)
    {
        return type.Properties.Where(p => p.TypeUsage.EdmType is SimpleType && p.DeclaringType == type && p.DefaultValue != null);
    }

    public IEnumerable<NavigationProperty> GetNavigationProperties(EntityType type)
    {
        return type.NavigationProperties.Where(np => np.DeclaringType == type);
    }
   
    public IEnumerable<NavigationProperty> GetCollectionNavigationProperties(EntityType type)
    {
        return type.NavigationProperties.Where(np => np.DeclaringType == type && np.ToEndMember.RelationshipMultiplicity == RelationshipMultiplicity.Many);
    }
   
    public FunctionParameter GetReturnParameter(EdmFunction edmFunction)
    {
        ArgumentNotNull(edmFunction, "edmFunction");

        var returnParamsProperty = edmFunction.GetType().GetProperty("ReturnParameters");
        return returnParamsProperty == null
            ? edmFunction.ReturnParameter
            : ((IEnumerable<FunctionParameter>)returnParamsProperty.GetValue(edmFunction, null)).FirstOrDefault();
    }

    public bool IsComposable(EdmFunction edmFunction)
    {
        ArgumentNotNull(edmFunction, "edmFunction");

        var isComposableProperty = edmFunction.GetType().GetProperty("IsComposableAttribute");
        return isComposableProperty != null && (bool)isComposableProperty.GetValue(edmFunction, null);
    }

    public IEnumerable<FunctionImportParameter> GetParameters(EdmFunction edmFunction)
    {
        return FunctionImportParameter.Create(edmFunction.Parameters, _code, _ef);
    }

    public TypeUsage GetReturnType(EdmFunction edmFunction)
    {
        var returnParam = GetReturnParameter(edmFunction);
        return returnParam == null ? null : _ef.GetElementType(returnParam.TypeUsage);
    }
   
    public bool GenerateMergeOptionFunction(EdmFunction edmFunction, bool includeMergeOption)
    {
        var returnType = GetReturnType(edmFunction);
        return !includeMergeOption && returnType != null && returnType.EdmType.BuiltInTypeKind == BuiltInTypeKind.EntityType;
    }
}

public static void ArgumentNotNull<T>(T arg, string name) where T : class
{
    if (arg == null)
    {
        throw new ArgumentNullException(name);
    }
}
#>