c# - How can I get the correct text definition of a generic type using reflection?

Question

I am working on code generation and ran into a snag with generics. Here is a "simplified" version of what is causing me issues.

Dictionary<string, DateTime> dictionary = new Dictionary<string, DateTime>();
string text = dictionary.GetType().FullName;

With the above code snippet the value of text is as follows:

 System.Collections.Generic.Dictionary`2[[System.String, mscorlib, Version=2.0.0.0, 
 Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.DateTime, mscorlib, 
 Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]

(Line breaks added for better readability.)

Is there a way to get the type name (type) in a different format without parsing the above string? I desire the following result for text:

System.Collections.Generic.Dictionary<System.String, System.DateTime>

Answer 1

There is no built-in way to get this representation in the .Net Framework. Namely because there is no way to get it correct. There are a good number of constructs that are not representable in C# style syntax. For instance "<>foo" is a valid type name in IL but cannot be represented in C#.

However, if you're looking for a pretty good solution it can be hand implemented fairly quickly. The below solution will work for most situations. It will not handle

1. Nested Types
2. Illegal C# Names
3. Couple of other scenarios

Example:

public static string GetFriendlyTypeName(Type type) {
    if (type.IsGenericParameter)
    {
        return type.Name;
    }

    if (!type.IsGenericType)
    {
        return type.FullName;
    }

    var builder = new System.Text.StringBuilder();
    var name = type.Name;
    var index = name.IndexOf("`");
    builder.AppendFormat("{0}.{1}", type.Namespace, name.Substring(0, index));
    builder.Append('<');
    var first = true;
    foreach (var arg in type.GetGenericArguments())
    {
        if (!first)
        {
            builder.Append(',');
        }
        builder.Append(GetFriendlyTypeName(arg));
        first = false;
    }
    builder.Append('>');
    return builder.ToString();
}