Uniform method to convert data types

Question

.NET knows many ways to convert data types:

• Convert-class;
• Functions inside a type like (Try)Parse and ToString, etc.;
• Implementation of interface IConvertable;
• The TypeConverter;
• The implicit and explicit conversion operator;
• Am I missing another one?

So if am converting one datatype to another, I need to know both types and I need to know which conversion method to use. And this becomes pretty nasty if one of those two types (or both) is a generic type.

So my question is: I there is uniform (generic) way in .NET to convert one data type to another, which might use all the other limited methods?

Answer 1

A good, generic way to convert between types is with Convert.ChangeType. Here's an example of how you could use it to write a generic converting method:

public static TResult Convert<TResult>(IConvertible source)
{
    return (TResult)System.Convert.ChangeType(source, typeof(TResult));
}

It, like other Convert methods, internally calls the IConvertible interface.

This will not make use of your other conversion options:

• The most common I'd think would be ToString; for that, you could add a check to see if TResult is string and if so, (after appropriate null checks) simply call ToString on your input.
• Using reflection you could check for:
  • the TypeConverterAttribute (TypeDescriptor.GetConverter seems to be the way to go from there)
  • (Try)Parse methods, (which you'd invoke), and
  • implicit/explicit conversion operators (the methods op_Implicit and op_Explicit, which you'd likewise invoke)

These are each fairly self-explanatory if you know a bit about reflection, but I could elaborate if any prove difficult.