C#.NET - Type.GetType(“System.Windows.Forms.Form”) returns null

问题

I have a snippet of code in my application (which references System.Windows.Forms) which attempts to resolve type information for a Form class like so:

Type tForm = Type.GetType("System.Windows.Forms.Form");
dynamic instance = Activator.CreateInstance(tForm);

but Activator.CreateInstance fails because tForm is null.

How do I solve this?

EDIT: Types MUST be resolvable at runtime!

回答1:

You need to use assembly-qualified name of the type

Type tForm = Type.GetType("System.Windows.Forms.Form, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089");

回答2:

Check this Jon Skeet answer on this : https://stackoverflow.com/a/3758295/314488

using System;
using System.Windows.Forms;

class Test
{
    static void Main()
    {
        string name = typeof(Form).AssemblyQualifiedName;
        Console.WriteLine(name);

        Type type = Type.GetType(name);
        Console.WriteLine(type);
    }
}
Output:

System.Windows.Forms.Form, System.Windows.Forms, Version=4.0.0.0, Culture=neutral,
PublicKeyToken=b77a5c561934e089
System.Windows.Forms.Form

Note that if you're using a strongly named assembly (like Form in this case) you must include all the assembly information - versioning, public key token etc.

回答3:

Type.GetType(string) checks a few different things: if the string passed includes assembly information, then it will look there. Otherwise, the calling assembly and a few other system assemblies are checked (probably System and mscorlib). It does not check every assembly.

So, you have a few options:

include the assembly information in the string, i.e. "Namespace.TypeName, AssemblyName"
use assembly.GetType(string), where assembly is the correct assembly
manually loop over all the assemblies loaded in the current AppDomain, checking each in turn

来源：https://stackoverflow.com/questions/13048171/c-net-type-gettypesystem-windows-forms-form-returns-null

标签

.net

reflection

types