如何查找和调用特定类型的.Net TypeConverter？

我想实现一个通用的运行时类型转换函数，它使用.Net TypeConverters来进行转换。

有谁知道如何查找和调用特定类型的TypeConverter？

考虑一下这个C＃示例：

// // Convert obj to the type specified by 'toType'. // object ConvertTo(object obj, Type toType) { if (TypeIsEqualOrDerivesFrom(obj.GetType(), toType)) <-- I know how to implement this. { // The type of obj is the same as the type specified by 'toType' or // the type of obj derives from the type specified by 'toType'. return obj; } if (TypeConverterExists(obj.GetType(), toType) <-- How do I implement this? { // There exists a type convertor that is capable of converting from // the type of obj to the type specified by 'toType'. return InvokeTypeConverter(obj, toType); <-- How do I implement this? } throw new TypeConversionFailedException(); } 

Answer 1

  TypeConverter converter = TypeDescriptor.GetConverter(sourceType); if(converter.CanConvertTo(destinationType)) { return converter.ConvertTo(obj, destinationType); } converter = TypeDescriptor.GetConverter(destinationType); if(converter.CanConvertFrom(sourceType)) { return converter.ConvertFrom(obj); } 

您还可以查看Convert.ChangeType(obj, destinationType)

Answer 2

这是我们现有应用程序中使用的代码…不确定它是否理想，但它对我们很有用。

 /// 
 /// Attempts to convert a value using any customer TypeConverters applied to the member /// 
 /// Object containing the value to be assigned /// Member to be assigned to ///  converted to the appropriate type public static Object CustomTypeConversion ( object value, MemberInfo member ) { if ( value == null || value == DBNull.Value ) return value; if ( member == null ) throw new ArgumentNullException ( ); List converters = GetCustomTypeConverters ( member ); foreach ( TypeConverter c in converters ) { if ( c.CanConvertFrom ( value.GetType ( ) ) ) return c.ConvertFrom ( value ); } if ( member is PropertyInfo ) { PropertyInfo prop = member as PropertyInfo; return ConvertToNative( value , prop.PropertyType ); } return ConvertToNative ( value, member.MemberType.GetType ( ) ); } /// 
 /// Extracts and instantiates any customer type converters assigned to a /// derivitive of the  property /// 
 /// Any class deriving from MemberInfo /// A list of customer type converters, empty if none found public static List GetCustomTypeConverters ( System.Reflection.MemberInfo member ) { List result = new List(); try { foreach ( TypeConverterAttribute a in member.GetCustomAttributes( typeof( TypeConverterAttribute ) , true ) ) { TypeConverter converter = Activator.CreateInstance( Type.GetType( a.ConverterTypeName ) ) as TypeConverter; if ( converter != null ) result.Add( converter ); } } catch { // Let it go, there were no custom converters } return result; } /// 
 /// Attempts to cast the incoming database field to the property type /// 
 /// Database value to cast /// Type to cast to /// The converted value, if conversion failed the original value will be returned public static object ConvertToNative ( object value , Type castTo ) { try { return Convert.ChangeType( value , castTo , System.Threading.Thread.CurrentThread.CurrentCulture ); } catch { return value; } } 

只需调用CustomTypeConversion方法然后你就可以了……可能比你需要的多一点但是彻底不是犯罪（或者是它？）。

Answer 3

除了Marc的回答之外，您可能会认为ASP.NET的ViewState与您要求的function类似。 它试图找到最有效的转换。

可能值得一看这个页面 ，也可能是这个 。

Answer 4

我不知道它有多强大，但我有时会将此代码用于generics类型转换：

 public T ConvertTo(object value) { return (T)Convert.ChangeType(value, typeof(T)); } 

我不知道ChangeType方法是否使用TypeConverters …