Bewerken

Share via

TypeConverter Class

  • Reference

Definition

Namespace:
System.ComponentModel
Assembly:
System.ComponentModel.TypeConverter.dll
Assembly:
System.dll
Assembly:
netstandard.dll
Source:
TypeConverter.cs
Source:
TypeConverter.cs
Source:
TypeConverter.cs

Provides a unified way of converting types of values to other types, as well as for accessing standard values and subproperties.

public ref class TypeConverter
public class TypeConverter
[System.Runtime.InteropServices.ComVisible(true)]
public class TypeConverter
type TypeConverter = class
[<System.Runtime.InteropServices.ComVisible(true)>]
type TypeConverter = class
Public Class TypeConverter
Inheritance
Object
TypeConverter
Derived
Attributes
ComVisibleAttribute

Examples

The following code example shows how to create an instance of a type converter and bind it to a class. The class implementing the converter, MyClassConverter, must inherit from the TypeConverter class.

public:
   [TypeConverter(Sample::MyClassConverter::typeid)]
   ref class MyClass
   {
      // Insert code here.
   };

[TypeConverter(typeof(MyClassConverter))]
 public class MyClass {
    // Insert code here.
}

<TypeConverter(GetType(MyClassConverter))> _
Public Class Class1
    ' Insert code here.
End Class

When you have a property that has an enumeration, check to see whether an enumeration value is valid before setting the property. The next code example requires that an enumeration called MyPropertyEnum has been declared.

public:
   property MyPropertyEnum MyProperty 
   {
      void set( MyPropertyEnum value )
      {
         // Checks to see if the value passed is valid.
         if ( !TypeDescriptor::GetConverter( MyPropertyEnum::typeid )->IsValid( value ) )
         {
            throw gcnew ArgumentException;
         }
         // The value is valid. Insert code to set the property.
      }
   }

public MyPropertyEnum MyProperty {
    set {
       // Checks to see if the value passed is valid.
       if (!TypeDescriptor.GetConverter(typeof(MyPropertyEnum)).IsValid(value)) {
          throw new ArgumentException();
       }
       // The value is valid. Insert code to set the property.
    }
 }


Public WriteOnly Property MyProperty() As MyPropertyEnum
    Set
        ' Checks to see if the value passed is valid.
        If Not TypeDescriptor.GetConverter(GetType(MyPropertyEnum)).IsValid(value) Then
            Throw New ArgumentException()
        End If
        ' The value is valid. Insert code to set the property.
    End Set 
End Property

Another common type converter usage is to convert an object to a string. The following code example prints out the name of the Color stored in the variable c.

Color c = Color::Red;
Console::WriteLine( TypeDescriptor::GetConverter( c )->ConvertToString( c ) );

Color c = Color.Red;
    Console.WriteLine(TypeDescriptor.GetConverter(typeof(Color)).ConvertToString(c));

Dim c As Color = Color.Red
Console.WriteLine(TypeDescriptor.GetConverter(c).ConvertToString(c))

You can also use a type converter to convert a value from its name, as shown in the next code example.

Color c =  (Color)(TypeDescriptor::GetConverter( Color::typeid )->ConvertFromString( "Red" ));

Color c = (Color)TypeDescriptor.GetConverter(typeof(Color)).ConvertFromString("Red");

Dim c As Color = CType(TypeDescriptor.GetConverter(GetType(Color)).ConvertFromString("Red"), Color)

In the following code example, you can use a type converter to print out the set of standard values that the object supports.

for each ( Color c in TypeDescriptor::GetConverter( Color::typeid )->GetStandardValues() )
{
   Console::WriteLine( TypeDescriptor::GetConverter( c )->ConvertToString( c ) );
}

foreach(Color c in TypeDescriptor.GetConverter(typeof(Color)).GetStandardValues()) {
    Console.WriteLine(TypeDescriptor.GetConverter(c).ConvertToString(c));
 }

Dim c As Color
For Each c In  TypeDescriptor.GetConverter(GetType(Color)).GetStandardValues()
    Console.WriteLine(TypeDescriptor.GetConverter(c).ConvertToString(c))
Next c

Remarks

The most common type of converter is one that converts to and from a text representation. The type converter for a class is bound to the class with a TypeConverterAttribute. Unless this attribute is overridden, all classes that inherit from this class use the same type converter as the base class.

Note

For general type system purposes, do not access a type converter directly. Instead, access the appropriate converter by using TypeDescriptor. For more information, see the code examples provided.

However, when using XAML, a XAML processor searches for the TypeConverterAttribute directly, instead of going through TypeDescriptor. For cases where you do want a TypeDescriptor instance from code, or where you create a shared instance in WPF resources, it is acceptable to construct it directly without referencing TypeDescriptor or other reflection and type system support.

Classes derived from TypeConverter are often referenced as part of how a XAML processor converts an attribute or initialization text value from markup (which is inherently a string) and generates an object for a run-time representation. Custom type authors that intend to support a type conversion behavior for XAML typically implement a TypeConverter class that supports their own unique ConvertFrom behavior from a string. This behavior enables type conversion from the string provided as a XAML attribute value and provides a XAML processor with the support needed to create an object from the string, so that the object can be produced in a parsed object graph. Custom types or members of custom types are indicated by applying TypeConverterAttribute to the definitions, with the attribute referencing the custom TypeConverter implementation. For more information, see Type Converters for XAML Overview.

Notes to Inheritors

Inherit from TypeConverter to implement your own conversion requirements. When you inherit from this class, you can override the following methods:

Note: Your derived type might be marked as internal or private, but an instance of your type can be created with the TypeDescriptor class. Do not write insecure code by assuming the caller is trusted. Assume instead that callers might create instances of your type in partial trust.

For more information about type converters for general (non-XAML) purposes, see How to: Implement a Type Converter or Generalized Type Conversion.

Constructors

TypeConverter()

Initializes a new instance of the TypeConverter class.

Methods

CanConvertFrom(ITypeDescriptorContext, Type)

Returns whether this converter can convert an object of the given type to the type of this converter, using the specified context.
CanConvertFrom(Type)

Returns whether this converter can convert an object of the given type to the type of this converter.
CanConvertTo(ITypeDescriptorContext, Type)

Returns whether this converter can convert the object to the specified type, using the specified context.
CanConvertTo(Type)

Returns whether this converter can convert the object to the specified type.
ConvertFrom(ITypeDescriptorContext, CultureInfo, Object)

Converts the given object to the type of this converter, using the specified context and culture information.
ConvertFrom(Object)

Converts the given value to the type of this converter.
ConvertFromInvariantString(ITypeDescriptorContext, String)

Converts the given string to the type of this converter, using the invariant culture and the specified context.
ConvertFromInvariantString(String)

Converts the given string to the type of this converter, using the invariant culture.
ConvertFromString(ITypeDescriptorContext, CultureInfo, String)

Converts the given text to an object, using the specified context and culture information.
ConvertFromString(ITypeDescriptorContext, String)

Converts the given text to an object, using the specified context.
ConvertFromString(String)

Converts the specified text to an object.
ConvertTo(ITypeDescriptorContext, CultureInfo, Object, Type)

Converts the given value object to the specified type, using the specified context and culture information.
ConvertTo(Object, Type)

Converts the given value object to the specified type, using the arguments.
ConvertToInvariantString(ITypeDescriptorContext, Object)

Converts the specified value to a culture-invariant string representation, using the specified context.
ConvertToInvariantString(Object)

Converts the specified value to a culture-invariant string representation.
ConvertToString(ITypeDescriptorContext, CultureInfo, Object)

Converts the given value to a string representation, using the specified context and culture information.
ConvertToString(ITypeDescriptorContext, Object)

Converts the given value to a string representation, using the given context.
ConvertToString(Object)

Converts the specified value to a string representation.
CreateInstance(IDictionary)

Re-creates an Object given a set of property values for the object.
CreateInstance(ITypeDescriptorContext, IDictionary)

Creates an instance of the type that this TypeConverter is associated with, using the specified context, given a set of property values for the object.
Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetConvertFromException(Object)

Returns an exception to throw when a conversion cannot be performed.
GetConvertToException(Object, Type)

Returns an exception to throw when a conversion cannot be performed.
GetCreateInstanceSupported()

Returns whether changing a value on this object requires a call to the CreateInstance(IDictionary) method to create a new value.
GetCreateInstanceSupported(ITypeDescriptorContext)

Returns whether changing a value on this object requires a call to CreateInstance(IDictionary) to create a new value, using the specified context.
GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetProperties(ITypeDescriptorContext, Object)

Returns a collection of properties for the type of array specified by the value parameter, using the specified context.
GetProperties(ITypeDescriptorContext, Object, Attribute[])

Returns a collection of properties for the type of array specified by the value parameter, using the specified context and attributes.
GetProperties(Object)

Returns a collection of properties for the type of array specified by the value parameter.
GetPropertiesSupported()

Returns whether this object supports properties.
GetPropertiesSupported(ITypeDescriptorContext)

Returns whether this object supports properties, using the specified context.
GetStandardValues()

Returns a collection of standard values from the default context for the data type this type converter is designed for.
GetStandardValues(ITypeDescriptorContext)

Returns a collection of standard values for the data type this type converter is designed for when provided with a format context.
GetStandardValuesExclusive()

Returns whether the collection of standard values returned from GetStandardValues() is an exclusive list.
GetStandardValuesExclusive(ITypeDescriptorContext)

Returns whether the collection of standard values returned from GetStandardValues() is an exclusive list of possible values, using the specified context.
GetStandardValuesSupported()

Returns whether this object supports a standard set of values that can be picked from a list.
GetStandardValuesSupported(ITypeDescriptorContext)

Returns whether this object supports a standard set of values that can be picked from a list, using the specified context.
GetType()

Gets the Type of the current instance.

(Inherited from Object)
IsValid(ITypeDescriptorContext, Object)

Returns whether the given value object is valid for this type and for the specified context.
IsValid(Object)

Returns whether the given value object is valid for this type.
MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
SortProperties(PropertyDescriptorCollection, String[])

Sorts a collection of properties.
ToString()

Returns a string that represents the current object.

(Inherited from Object)

Applies to

See also