Critical Problem with Sharepoint Timer Job Properties

Some minutes ago I tried to create a time job

A added some properties like

this.Properties.Add("fileName"开发者_如何学JAVA, fileName); this.Properties.Add("username", new NetworkCredential("username", "passworD");

After updating the job a get a critical error in the Timer Job list of the Central Administration occured.

The platform does not know how to deserialize an object of type System.Net.NetworkCredential. The platform can deserialize primitive types such as strings, integers, and GUIDs; other SPPersistedObjects or SPAutoserializingObjects; or collections of any of the above. Consider redesigning your objects to store values in one of these supported formats, or contact your software vendor for support.

Now Im unabled to delete or retract the job with SPJobdefinition's Delete() method or other classes within the SPObject model.

Ok. I got it. I deleted the corresponding object in the SharepointConfigDatabase.dbo.Objects table