FieldBuilder Class

Definition

Namespace:

System.Reflection.Emit

Assembly:

System.Reflection.Emit.dll

Source:

FieldBuilder.cs

Defines and represents a field. This class cannot be inherited.

public ref class FieldBuilder abstract : System::Reflection::FieldInfo

public abstract class FieldBuilder : System.Reflection.FieldInfo

type FieldBuilder = class
    inherit FieldInfo

Public MustInherit Class FieldBuilder
Inherits FieldInfo

Inheritance

Object

MemberInfo

FieldInfo

FieldBuilder

Examples

The following example illustrates the use of the FieldBuilder class.

using System;
using System.Reflection;
using System.Reflection.Emit;

public class FieldBuilder_Sample
{
    private static Type? CreateType()
    {
        // Create an assembly.
        AssemblyName assemName = new AssemblyName();
        assemName.Name = "DynamicAssembly";
        AssemblyBuilder assemBuilder =
                       AssemblyBuilder.DefineDynamicAssembly(assemName, AssemblyBuilderAccess.Run);
        // Create a dynamic module in Dynamic Assembly.
        ModuleBuilder modBuilder = assemBuilder.DefineDynamicModule("DynamicModule");
        // Define a public class named "DynamicClass" in the assembly.
        TypeBuilder typBuilder = modBuilder.DefineType("DynamicClass", TypeAttributes.Public);

        // Define a private String field named "DynamicField" in the type.
        FieldBuilder fldBuilder = typBuilder.DefineField("DynamicField",
            typeof(string), FieldAttributes.Private | FieldAttributes.Static);
        // Create the constructor.
        Type[] constructorArgs = { typeof(String) };
        ConstructorBuilder constructor = typBuilder.DefineConstructor(
           MethodAttributes.Public, CallingConventions.Standard, constructorArgs);
        ILGenerator constructorIL = constructor.GetILGenerator();
        constructorIL.Emit(OpCodes.Ldarg_0);
        ConstructorInfo? superConstructor = typeof(Object).GetConstructor(new Type[0]);
        constructorIL.Emit(OpCodes.Call, superConstructor!);
        constructorIL.Emit(OpCodes.Ldarg_0);
        constructorIL.Emit(OpCodes.Ldarg_1);
        constructorIL.Emit(OpCodes.Stfld, fldBuilder);
        constructorIL.Emit(OpCodes.Ret);

        // Create the DynamicMethod method.
        MethodBuilder methBuilder = typBuilder.DefineMethod("DynamicMethod",
                             MethodAttributes.Public, typeof(String), null);
        ILGenerator methodIL = methBuilder.GetILGenerator();
        methodIL.Emit(OpCodes.Ldarg_0);
        methodIL.Emit(OpCodes.Ldfld, fldBuilder);
        methodIL.Emit(OpCodes.Ret);

        Console.WriteLine($"Name               : {fldBuilder.Name}");
        Console.WriteLine($"DeclaringType      : {fldBuilder.DeclaringType}");
        Console.WriteLine($"Type               : {fldBuilder.FieldType}");
        return typBuilder.CreateType();
    }

    public static void Main()
    {
        Type? dynType = CreateType();
        try
        {
            if (dynType is not null)
            {
                // Create an instance of the "HelloWorld" class.
                Object? helloWorld = Activator.CreateInstance(dynType, new Object[] { "HelloWorld" });
                // Invoke the "DynamicMethod" method of the "DynamicClass" class.
                Object? obj = dynType.InvokeMember("DynamicMethod",
                               BindingFlags.InvokeMethod, null, helloWorld, null);
                Console.WriteLine($"DynamicClass.DynamicMethod returned: \"{obj}\"");
            }
        }
        catch (MethodAccessException e)
        {
            Console.WriteLine($"{e.GetType().Name}: {e.Message}");
        }
    }
}

Imports System.Reflection
Imports System.Reflection.Emit

Public Module FieldBuilder_Sample
   Private Function CreateType() As Type
      ' Create an assembly.
      Dim assemName As New AssemblyName()
      assemName.Name = "DynamicAssembly"
      Dim assemBuilder As AssemblyBuilder = AssemblyBuilder.DefineDynamicAssembly(assemName,
                                                AssemblyBuilderAccess.Run)
      ' Create a dynamic module in Dynamic Assembly.
      Dim modBuilder As ModuleBuilder = assemBuilder.DefineDynamicModule("DynamicModule")
      ' Define a public class named "DynamicClass" in the assembly.
      Dim typBuilder As TypeBuilder = modBuilder.DefineType("DynamicClass", 
                                          TypeAttributes.Public)
      ' Define a private String field named "DynamicField" in the type.
      Dim fldBuilder As FieldBuilder = typBuilder.DefineField("DynamicField",
                  GetType(String), FieldAttributes.Private Or FieldAttributes.Static)
      ' Create the constructor.
      Dim constructorArgs As Type() = {GetType(String)}
      Dim constructor As ConstructorBuilder = 
                  typBuilder.DefineConstructor(MethodAttributes.Public, 
                           CallingConventions.Standard, constructorArgs)
      Dim constructorIL As ILGenerator = constructor.GetILGenerator()
      constructorIL.Emit(OpCodes.Ldarg_0)
      Dim superConstructor As ConstructorInfo = GetType(Object).GetConstructor(New Type() {})
      constructorIL.Emit(OpCodes.Call, superConstructor)
      constructorIL.Emit(OpCodes.Ldarg_0)
      constructorIL.Emit(OpCodes.Ldarg_1)
      constructorIL.Emit(OpCodes.Stfld, fldBuilder)
      constructorIL.Emit(OpCodes.Ret)

      ' Create the DynamicMethod method.
      Dim methBuilder As MethodBuilder = typBuilder.DefineMethod("DynamicMethod", 
                        MethodAttributes.Public, GetType(String), Nothing)
      Dim methodIL As ILGenerator = methBuilder.GetILGenerator()
      methodIL.Emit(OpCodes.Ldarg_0)
      methodIL.Emit(OpCodes.Ldfld, fldBuilder)
      methodIL.Emit(OpCodes.Ret)

      Console.WriteLine($"Name               : {fldBuilder.Name}")
      Console.WriteLine($"DeclaringType      : {fldBuilder.DeclaringType}")
      Console.WriteLine($"Type               : {fldBuilder.FieldType}")
      Return typBuilder.CreateType()
   End Function 

   Public Sub Main()
      Dim dynType As Type = CreateType()
      Try  
        ' Create an instance of the "HelloWorld" class.
         Dim helloWorld As Object = Activator.CreateInstance(dynType, New Object() {"HelloWorld"})
         ' Invoke the "DynamicMethod" method of the "DynamicClass" class.
         Dim obj As Object = dynType.InvokeMember("DynamicMethod", 
                  BindingFlags.InvokeMethod, Nothing, helloWorld, Nothing)
         Console.WriteLine($"DynamicClass.DynamicMethod returned: ""{obj}""")
      Catch e As MethodAccessException
            Console.WriteLine($"{e.GetType().Name}: {e.Message}")
      End Try
   End Sub 
End Module

Remarks

Get an instance of FieldBuilder by calling DefineField, DefineInitializedData, or DefineUninitializedData.

Note

The SetValue method is currently not supported. As a workaround, retrieve the FieldInfo by reflecting on the finished type and call SetValue to set the value of the field.

Constructors

FieldBuilder()

Initializes a new instance of the FieldBuilder class.

Properties

Attributes	Indicates the attributes of this field. This property is read-only.
CustomAttributes	Gets a collection that contains this member's custom attributes. (Inherited from MemberInfo)
DeclaringType	Indicates a reference to the Type object for the type that declares this field. This property is read-only.
FieldHandle	Indicates the internal metadata handle for this field. This property is read-only.
FieldType	Indicates the Type object that represents the type of this field. This property is read-only.
IsAssembly	Gets a value indicating whether the potential visibility of this field is described by Assembly; that is, the field is visible at most to other types in the same assembly, and is not visible to derived types outside the assembly. (Inherited from FieldInfo)
IsCollectible	Gets a value that indicates whether this MemberInfo object is part of an assembly held in a collectible AssemblyLoadContext. (Inherited from MemberInfo)
IsFamily	Gets a value indicating whether the visibility of this field is described by Family; that is, the field is visible only within its class and derived classes. (Inherited from FieldInfo)
IsFamilyAndAssembly	Gets a value indicating whether the visibility of this field is described by FamANDAssem; that is, the field can be accessed from derived classes, but only if they are in the same assembly. (Inherited from FieldInfo)
IsFamilyOrAssembly	Gets a value indicating whether the potential visibility of this field is described by FamORAssem; that is, the field can be accessed by derived classes wherever they are, and by classes in the same assembly. (Inherited from FieldInfo)
IsInitOnly	Gets a value indicating whether the field can only be set in the body of the constructor. (Inherited from FieldInfo)
IsLiteral	Gets a value indicating whether the value is written at compile time and cannot be changed. (Inherited from FieldInfo)
IsNotSerialized	Obsolete. Gets a value indicating whether this field has the NotSerialized attribute. (Inherited from FieldInfo)
IsPinvokeImpl	Gets a value indicating whether the corresponding PinvokeImpl attribute is set in FieldAttributes. (Inherited from FieldInfo)
IsPrivate	Gets a value indicating whether the field is private. (Inherited from FieldInfo)
IsPublic	Gets a value indicating whether the field is public. (Inherited from FieldInfo)
IsSecurityCritical	Gets a value that indicates whether the current field is security-critical or security-safe-critical at the current trust level. (Inherited from FieldInfo)
IsSecuritySafeCritical	Gets a value that indicates whether the current field is security-safe-critical at the current trust level. (Inherited from FieldInfo)
IsSecurityTransparent	Gets a value that indicates whether the current field is transparent at the current trust level. (Inherited from FieldInfo)
IsSpecialName	Gets a value indicating whether the corresponding SpecialName attribute is set in the FieldAttributes enumerator. (Inherited from FieldInfo)
IsStatic	Gets a value indicating whether the field is static. (Inherited from FieldInfo)
MemberType	Gets a MemberTypes value indicating that this member is a field. (Inherited from FieldInfo)
MetadataToken	Gets a token that identifies the current dynamic module in metadata.
Module	Gets the module in which the type that contains this field is being defined.
Name	Indicates the name of this field. This property is read-only.
ReflectedType	Indicates the reference to the Type object from which this object was obtained. This property is read-only.

Methods

Equals(Object)	Returns a value that indicates whether this instance is equal to a specified object. (Inherited from FieldInfo)
GetCustomAttributes(Boolean)	Returns all the custom attributes defined for this field.
GetCustomAttributes(Type, Boolean)	Returns all the custom attributes defined for this field identified by the given type.
GetCustomAttributesData()	Returns a list of CustomAttributeData objects representing data about the attributes that have been applied to the target member. (Inherited from MemberInfo)
GetHashCode()	Returns the hash code for this instance. (Inherited from FieldInfo)
GetModifiedFieldType()	Gets the modified type of this field object. (Inherited from FieldInfo)
GetOptionalCustomModifiers()	Gets an array of types that identify the optional custom modifiers of the field. (Inherited from FieldInfo)
GetRawConstantValue()	Returns a literal value associated with the field by a compiler. (Inherited from FieldInfo)
GetRequiredCustomModifiers()	Gets an array of types that identify the required custom modifiers of the property. (Inherited from FieldInfo)
GetType()	Discovers the attributes of a class field and provides access to field metadata. (Inherited from FieldInfo)
GetValue(Object)	Retrieves the value of the field supported by the given object.
GetValueDirect(TypedReference)	Returns the value of a field supported by a given object. (Inherited from FieldInfo)
HasSameMetadataDefinitionAs(MemberInfo)	(Inherited from MemberInfo)
IsDefined(Type, Boolean)	Indicates whether an attribute having the specified type is defined on a field.
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
SetConstant(Object)	Sets the default value of this field.
SetConstantCore(Object)	When overridden in a derived class, sets the default value of this field.
SetCustomAttribute(ConstructorInfo, Byte[])	Sets a custom attribute using a specified custom attribute blob.
SetCustomAttribute(CustomAttributeBuilder)	Sets a custom attribute using a custom attribute builder.
SetCustomAttributeCore(ConstructorInfo, ReadOnlySpan<Byte>)	When overridden in a derived class, sets a custom attribute on this assembly.
SetOffset(Int32)	Specifies the field layout.
SetOffsetCore(Int32)	When overridden in a derived class, specifies the field layout.
SetValue(Object, Object)	Sets the value of the field supported by the given object. (Inherited from FieldInfo)
SetValue(Object, Object, BindingFlags, Binder, CultureInfo)	Sets the value of the field supported by the given object.
SetValueDirect(TypedReference, Object)	Sets the value of the field supported by the given object. (Inherited from FieldInfo)
ToString()	Returns a string that represents the current object. (Inherited from Object)

Extension Methods

GetCustomAttribute(MemberInfo, Type)	Retrieves a custom attribute of a specified type that is applied to a specified member.
GetCustomAttribute(MemberInfo, Type, Boolean)	Retrieves a custom attribute of a specified type that is applied to a specified member, and optionally inspects the ancestors of that member.
GetCustomAttribute<T>(MemberInfo)	Retrieves a custom attribute of a specified type that is applied to a specified member.
GetCustomAttribute<T>(MemberInfo, Boolean)	Retrieves a custom attribute of a specified type that is applied to a specified member, and optionally inspects the ancestors of that member.
GetCustomAttributes(MemberInfo)	Retrieves a collection of custom attributes that are applied to a specified member.
GetCustomAttributes(MemberInfo, Boolean)	Retrieves a collection of custom attributes that are applied to a specified member, and optionally inspects the ancestors of that member.
GetCustomAttributes(MemberInfo, Type)	Retrieves a collection of custom attributes of a specified type that are applied to a specified member.
GetCustomAttributes(MemberInfo, Type, Boolean)	Retrieves a collection of custom attributes of a specified type that are applied to a specified member, and optionally inspects the ancestors of that member.
GetCustomAttributes<T>(MemberInfo)	Retrieves a collection of custom attributes of a specified type that are applied to a specified member.
GetCustomAttributes<T>(MemberInfo, Boolean)	Retrieves a collection of custom attributes of a specified type that are applied to a specified member, and optionally inspects the ancestors of that member.
IsDefined(MemberInfo, Type)	Indicates whether custom attributes of a specified type are applied to a specified member.
IsDefined(MemberInfo, Type, Boolean)	Indicates whether custom attributes of a specified type are applied to a specified member, and, optionally, applied to its ancestors.
GetMetadataToken(MemberInfo)	Gets a metadata token for the given member, if available.
HasMetadataToken(MemberInfo)	Returns a value that indicates whether a metadata token is available for the specified member.