TypeConverter | .NET Windows Forms in a Nutshell

TypeConverter

System.ComponentModel (system.dll)

class

This class provides a means to translate between one type and other representations of that typetypically a string representation. The designer environment uses type converters to translate between types it does not understand (for example, a System.Drawing.Size ) and one it can represent in a System.Windows.Forms.PropertyGrid (for example, a string).

One of the quickest and simplest ways to make your custom type available in a designer is to implement a TypeConverter for it and adorn it with a TypeConverterAttribute to bind the appropriate converter. For finer control, you can add the attribute to a particular property to change the type converter for that particular instance of the type.

To implement a TypeConverter you should override the CanConvertFrom() , CanConvertTo( ) , ConvertFrom() and ConvertTo() methods . At a minimum, you should implement conversion to and from a string, and you may also want to support InstanceDescriptor to support more complex initialization scenarios in design-time serialization.

If your object is immutable and requires recreation to modify it, you need to override CreateInstance() and GetCreateInstanceSupported() . This will be passed a System.Collections.IDictionary of property name /value pairs and optionally an ITypeDescriptorContext , which you may need to use in the conversion process.

If the type contains properties or you wish to extend it to appear to support properties of its own, you can override the GetProperties() and GetPropertiesSupported() methods. If you want add your own properties, derive them from SimplePropertyDescriptor (overriding the GetValue() and SetValue() methods.

A type can also support standard values (well-known values that can be assigned to the type). Implement GetStandardValues( ) and GetStandardValuesSupported() to provide standard values. If you also override GetStandardValuesExclusive() , you can indicate that the type will only accept one of the standard values.

 public class  TypeConverter  {  // Public Constructors  public  TypeConverter  ();  // Public Instance Methods  public virtual bool  CanConvertFrom  (ITypeDescriptorContext  context  , Type  sourceType  );    public bool  CanConvertFrom  (Type  sourceType  );    public virtual bool  CanConvertTo  (ITypeDescriptorContext  context  , Type  destinationType  );    public bool  CanConvertTo  (Type  destinationType  );    public virtual object  ConvertFrom  (ITypeDescriptorContext  context  , System.Globalization.CultureInfo  culture  , object  value  );    public object  ConvertFrom  (object  value  );    public object  ConvertFromInvariantString  (ITypeDescriptorContext  context  , string  text  );    public object  ConvertFromInvariantString  (string  text  );    public object  ConvertFromString  (ITypeDescriptorContext  context  , System.Globalization.CultureInfo  culture  , string  text  );    public object  ConvertFromString  (ITypeDescriptorContext  context  , string  text  );    public object  ConvertFromString  (string  text  );    public virtual object  ConvertTo  (ITypeDescriptorContext  context  , System.Globalization.CultureInfo  culture  ,          object  value  , Type  destinationType  );    public object  ConvertTo  (object  value  , Type  destinationType  );    public string  ConvertToInvariantString  (ITypeDescriptorContext  context  , object  value  );    public string  ConvertToInvariantString  (object  value  );    public string  ConvertToString  (ITypeDescriptorContext  context  , System.Globalization.CultureInfo  culture  , object  value  );    public string  ConvertToString  (ITypeDescriptorContext  context  , object  value  );    public string  ConvertToString  (object  value  );    public object  CreateInstance  (System.Collections.IDictionary  propertyValues  );    public virtual object  CreateInstance  (ITypeDescriptorContext  context  , System.Collections.IDictionary  propertyValues  );    public bool  GetCreateInstanceSupported  ();    public virtual bool  GetCreateInstanceSupported  (ITypeDescriptorContext  context  );    public PropertyDescriptorCollection  GetProperties  (ITypeDescriptorContext  context  , object  value  );    public virtual PropertyDescriptorCollection  GetProperties  (ITypeDescriptorContext  context  , object  value  ,          Attribute[]  attributes  );    public PropertyDescriptorCollection  GetProperties  (ITypeDescriptorContext  context  , object  value  , object  value  );    public bool  GetPropertiesSupported  ();    public virtual bool  GetPropertiesSupported  (ITypeDescriptorContext  context  );    public ICollection  GetStandardValues  ();    public virtual StandardValuesCollection  GetStandardValues  (ITypeDescriptorContext  context  );    public bool  GetStandardValuesExclusive  ();    public virtual bool  GetStandardValuesExclusive  (ITypeDescriptorContext  context  );    public bool  GetStandardValuesSupported  ();    public virtual bool  GetStandardValuesSupported  (ITypeDescriptorContext  context  );    public virtual bool  IsValid  (ITypeDescriptorContext  context  , object  value  );    public bool  IsValid  (object  value  );  // Protected Instance Methods  protected Exception  GetConvertFromException  (object  value  );    protected Exception  GetConvertToException  (object  value  , Type  destinationType  );    protected PropertyDescriptorCollection  SortProperties  (PropertyDescriptorCollection  props  , string[]  names  ); }

Subclasses

Multiple types

Returned By

IComNativeDescriptorHandler.GetConverter() , ICustomTypeDescriptor.GetConverter() , PropertyDescriptor.Converter , TypeDescriptor.GetConverter()