/// <summary>
/// 查找最精确的输入类型和类型转换方法。
/// </summary>
/// <param name="method">类型转换方法。</param>
/// <param name="inputRelation">实际输入类型到方法输入类型间的关系。</param>
/// <param name="outputRelation">实际输出类型到方法输出类型间的关系。</param>
private void GetBestConversion(UserConversionMethod method, TypeRelation inputRelation, TypeRelation outputRelation)
{
Contract.Requires(method != null);
// 更新最优输入和输出类型。
UpdateBestType(method.InputType, inputRelation, true, ref bestInputType, ref bestInputRelation);
UpdateBestType(method.OutputType, outputRelation, false, ref bestOutputType, ref bestOutputRelation);
if (method.InputType == bestInputType && method.OutputType == bestOutputType)
{
bestMethod.Value = method;
}
}
/// <summary>
/// 在 <paramref name="basicType"/> 类型中寻找能够将对象从 <paramref name="inputType"/> 类型转换为
/// <paramref name="basicType"/> 类型的用户自定义类型转换方法。
/// 需要保证 <paramref name="basicType"/> 中存在用户自定义类型转换方法。
/// </summary>
/// <param name="inputType">要转换的对象的类型。</param>
/// <param name="basicType">要寻找自定义类型转换方法的类型。</param>
/// <returns>将对象从 <paramref name="inputType"/> 类型转换为 <paramref name="basicType"/>
/// 类型的用户自定义类型转换方法。如果不存在则为 <c>null</c>。</returns>
public static MethodInfo GetConversionFrom(Type basicType, Type inputType)
{
Contract.Requires(inputType != null && basicType != null);
UserConversions convs = GetUserConversions(basicType);
for (int i = 0; i < convs.ConvertToIndex; i++)
{
UserConversionMethod method = convs.Methods[i];
if (method.InputType == inputType)
{
return(method.Method);
}
}
return(null);
}
/// <summary>
/// 在 <paramref name="basicType"/> 类型中寻找能够将对象从 <paramref name="basicType"/> 类型转换为
/// <paramref name="outputType"/> 类型的用户自定义类型转换方法。
/// 需要保证 <paramref name="basicType"/> 中存在用户自定义类型转换方法。
/// </summary>
/// <param name="basicType">要寻找自定义类型转换方法的类型。</param>
/// <param name="outputType">要转换到的对象的类型。</param>
/// <returns>将对象从 <paramref name="basicType"/> 类型转换为 <paramref name="outputType"/>
/// 类型的用户自定义类型转换方法。如果不存在则为 <c>null</c>。</returns>
public static MethodInfo GetConversionTo(Type basicType, Type outputType)
{
Contract.Requires(outputType != null && basicType != null);
UserConversions convs = GetUserConversions(basicType);
Contract.Assume(convs.ConvertToIndex >= 0);
for (int i = convs.ConvertToIndex; i < convs.Methods.Length; i++)
{
UserConversionMethod method = convs.Methods[i];
if (method.OutputType == outputType)
{
return(method.Method);
}
}
return(null);
}
/// <summary>
/// 查找合适的用户自定义类型转换方法。
/// </summary>
/// <returns>合适的用户自定义类型转换方法，如果不存在则为 <c>null</c>。</returns>
public MethodInfo FindConversion()
{
UserConversions convs = GetUserConversions(inputType);
if (convs != null)
{
Contract.Assume(convs.ConvertToIndex >= 0);
for (int i = convs.ConvertToIndex; i < convs.Methods.Length; i++)
{
UserConversionMethod method = convs.Methods[i];
ConversionType ctype = ConversionFactory.GetStandardConversion(outputType, method.OutputType);
if (ctype == ConversionType.None)
{
continue;
}
TypeRelation inputRelation = (method.InputType == inputType) ?
TypeRelation.Best : TypeRelation.Second;
TypeRelation outputRelation = TypeRelation.Best;
if (ctype >= ConversionType.ExplicitNumeric)
{
outputRelation = TypeRelation.Second;
}
else if (ctype > ConversionType.Identity)
{
outputRelation = TypeRelation.Thirt;
}
GetBestConversion(method, inputRelation, outputRelation);
}
}
convs = GetUserConversions(outputType);
if (convs != null)
{
for (int i = 0; i < convs.ConvertToIndex; i++)
{
UserConversionMethod method = convs.Methods[i];
ConversionType ctype = ConversionFactory.GetStandardConversion(method.InputType, inputType);
if (ctype == ConversionType.None)
{
continue;
}
TypeRelation outputRelation = (method.OutputType == outputType) ?
TypeRelation.Best : TypeRelation.Second;
TypeRelation inputRelation = TypeRelation.Best;
if (ctype >= ConversionType.ExplicitNumeric)
{
inputRelation = TypeRelation.Second;
}
else if (ctype > ConversionType.Identity)
{
inputRelation = TypeRelation.Thirt;
}
GetBestConversion(method, inputRelation, outputRelation);
}
}
if (bestMethod.IsUnique)
{
return(bestMethod.Value.Method);
}
if (bestMethod.IsAmbig)
{
throw CommonExceptions.AmbiguousUserDefinedConverter(inputType, outputType);
}
return(null);
}
/// <summary>
/// 使用指定的类型转换方法列表和索引初始化 <see cref="UserConversions"/> 类的新实例。
/// </summary>
/// <param name="methods">类型转换方法列表。</param>
/// <param name="index">转换到方法在列表中的起始索引。</param>
public UserConversions(UserConversionMethod[] methods, int index)
{
Contract.Requires(methods != null && index >= 0 && index < methods.Length);
this.Methods = methods;
this.ConvertToIndex = index;
}
/// <summary>
/// 查找最精确的输入类型和类型转换方法。
/// </summary>
/// <param name="method">类型转换方法。</param>
/// <param name="inputRelation">实际输入类型到方法输入类型间的关系。</param>
/// <param name="outputRelation">实际输出类型到方法输出类型间的关系。</param>
private void GetBestConversion(UserConversionMethod method, TypeRelation inputRelation, TypeRelation outputRelation)
{
Contract.Requires(method != null);
// 更新最优输入和输出类型。
UpdateBestType(method.InputType, inputRelation, true, ref bestInputType, ref bestInputRelation);
UpdateBestType(method.OutputType, outputRelation, false, ref bestOutputType, ref bestOutputRelation);
if (method.InputType == bestInputType && method.OutputType == bestOutputType)
{
bestMethod.Value = method;
}
}