How to I convert from Type.FullName to a C# type name?

Question

Examples,

1. "Namespace.ClassName+NestedClassName" becomes "Namespace.ClassName.NestedClassName".
2. "System.Collections.Generic.List`1[System.String]" becomes "System.Collections.Generic.List".

I need this for a code generator and I don't want to do a simple RegEx replace because of edge cases such as type names with '+' symbols in them. (Yes, though stupid that is possible.)

Answer 1

    /// <summary>
    /// Gets the fully quantified name in C# format.
    /// </summary>
    public string CSharpFullName
    {
        get
        {
            if (m_CSharpFullName == null)
            {

                var result = new StringBuilder(m_TypeInfo.ToString().Length);
                BuildCSharpFullName(m_TypeInfo.AsType(), null, result);

                m_CSharpFullName = result.ToString();
            }
            return m_CSharpFullName;
        }
    }

    static void BuildCSharpFullName(Type typeInfo, List<Type> typeArgs, StringBuilder result)
    {
        var localTypeParamCount = typeInfo.GetTypeInfo().GenericTypeParameters.Length;
        var localTypeArgCount = typeInfo.GetTypeInfo().GenericTypeArguments.Length;

        var typeParamCount = Math.Max(localTypeParamCount, localTypeArgCount);

        if (typeArgs == null)
            typeArgs = new List<Type>(typeInfo.GetTypeInfo().GenericTypeArguments);


        if (typeInfo.IsNested)
        {
            BuildCSharpFullName(typeInfo.DeclaringType, typeArgs, result);
        }
        else
        {
            result.Append(typeInfo.Namespace);
        }

        result.Append(".");
        foreach (var c in typeInfo.Name)
        {
            if (c == '`') //we found a generic
                break;
            result.Append(c);
        }

        if (localTypeParamCount > 0)
        {
            result.Append("<");

            for (int i = 0; i < localTypeParamCount; i++)
            {
                if (i > 0)
                    result.Append(",");
                BuildCSharpFullName(typeArgs[i], null, result); //note that we are "eating" the typeArgs that we passed to us from the nested type.
            }
            typeArgs.RemoveRange(0, localTypeParamCount); //remove the used args


            result.Append(">");
        }
        else if (localTypeArgCount > 0 && typeArgs.Count > 0)
        {
            result.Append("<");

            for (int i = 0; i < Math.Min(localTypeArgCount, typeArgs.Count); i++)
            {
                if (i > 0)
                    result.Append(",");
                BuildCSharpFullName(typeArgs[i], null, result);
            }
            result.Append(">");
        }


    }

Answer 2

You could use Type.GetType to parse the string into a Type object. From there you could use GetGenericArguments and other members to get the Type info of the individual components. You could use those to reconstruct your target string.