Exception with System.Type.GetType(...) function

Syl20 wrote:

Hello all, I have a strange problem with the System.Type.GetType(...) function. When I do : try { string maChaine = "System.Windows.Forms.Button"; Type ty = Type.GetType(maChaine, true); } catch (Exception ex) { label1.Text = ex.Message; } An exception raises ; the message is (I translate ...) "Impossible to load the type System.Windows.Forms.Button from the assembly WindowsApplicationXXX, Version xxx, ... Why this exception ? Have you an idea ?

The reason for this is that you are using the short name for the type when calling GetType. If the type is not in MSCORLIB.dll, and it is not in the current assembly that you are making the call to GetType from, then you need to use the full type name (with assembly information) in order to get the type. Otherwise, the runtime doesn't know how to resolve the assembly to get the type.

Hope this helps.

- Nicholas Paldino [.NET/C# MVP]
- mvp@spam.guard.caspershouse.com

casperOne at 2007-8-21 >

Syl20 wrote:

Thanks for your reply, CasperOne. You mean "System.Windows.Forms.Button" is a short name ? I have added references to "System.Windows.Forms" but nothing change ... So how can I simply get a System.Type from the string "System.Windows.Forms.Button" ? Thanks a lot

Just because you have a reference to that assembly doesn't mean that the same type can't be defined elsewhere (and even in the same namespace, which is actually allowed if you load two assemblies with different versions at the same time).

The full name of the type is:

System.Windows.Forms.Button, System.Windows.Forms, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089

This is for the Button class in the System.Windows.Forms namespace in .NET 2.0 beta 1. If you are using another version, the version and public key token (I believe) will be different.

Also, if you want the fully qualified name, you can get the type for the object through GetType, and then call the AssemblyQualifiedName property to get the full name.

- Nicholas Paldino [.NET/C# MVP]
- mvp@spam.guard.caspershouse.com

casperOne at 2007-8-21 >

Syl20 wrote:

Thanks CasperOne. But : * I can't know the fully qualified name of the component, because the application will be deployed on many computers.

This has nothing to do with the component name. The assembly qualified name of the type has nothing to do with the machine that it is installed on.

Syl20 wrote:

* I can't use the GetType function on components, the string corresponding to the componend comes from a XML file.

This isn't a problem. You can easily find out the full name of the component by doing:

Console.WriteLine(typeof(System.Windows.Forms.Button).AssemblyQualifiedName);

You can then then paste that output into your XML file.

- Nicholas Paldino [.NET/C# MVP]
- mvp@spam.guard.caspershouse.com

casperOne at 2007-8-21 >

Chris J. Breisch wrote:

Can you do something like this? You're going to have to find some way to get the AssemblyQualifiedName. This is one way I thought of. try { string maChaine = "System.Windows.Forms.Button," +label1.GetType().Assembly.FullName; Type ty = Type.GetType(maChaine, true); label1.Text = ty.AssemblyQualifiedName; } catch (Exception ex) { label1.Text = ex.Message; }

You could do this, but generally speaking, it's a guess, because you don't know that a label won't be moved to another assembly (although in this case, it most likely never will, as a general purpose algorithm, it will break easily if types move between assemblies).

Also, generating your own fully qualified type names is a bad idea. It's best to let the framework handle them.

- Nicholas Paldino [.NET/C# MVP]
- mvp@spam.guard.caspershouse.com

casperOne at 2007-8-21 >

Assembly winForms = Assembly.Load("System.Windows.Forms); Type button = winForms.GetType("System.Windows.Forms.Button");

-Shawn

ShawnFarkas-MS at 2007-8-21 >