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DLL reference error when running project when using newer dll

Posted By:      Posted Date: December 04, 2010    Points: 0   Category :.NET Framework
I have a C# Class library project, it's simply a DLL that contains some custom reporting definition.

That DLL is referenced in a ASP.NET application, this setup worked for years, but recently, after fixing an error in the DLL, I started getting the following error :

System.Exception was unhandled by user code
 Message=System.IO.FileLoadException: Could not load file or assembly 'IReportDef, Version=, Culture=neutral, PublicKeyToken=ac2eee5c6b52ff89' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
File name: 'IReportDef, Version=, Culture=neutral, PublicKeyToken=ac2eee5c6b52ff89'
  at System.RuntimeTypeHandle._GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark, Boolean loadTypeFromPartialName)
  at System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark)
  at System.RuntimeType.PrivateGetType(String typeName, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark)
  at System.Type.GetType(String typeName)
  at System.Data.XSDSchema.SetProperties(Object instance, XmlAttribute[] attrs)
  at System.Data.XSDSchema.HandleElementColumn(XmlS

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