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Compiler Error CS0234

The type or namespace name 'name' does not exist in the namespace 'namespace' (are you missing an assembly reference?)

A type was expected. Possible reasons include:

  • An assembly that contains the definition of a type was not referenced in the compilation; use /reference (Import Metadata) to specify the assembly.

  • You passed a variable name to the typeof operator.

See Add Reference Dialog Box for information on how to add a reference in the development environment.

If you see this error after moving code from one development machine to another, make sure that the project on the new machine has the correct references, and that the versions of the assemblies are the same as on the old machine. You can also use the Object Browser to inspect an assembly and verify whether it contains the types that you expect it to contain.

The following sample generates CS0234:

// CS0234.cs
public class C
   public static void Main()
      System.DateTime x = new System.DateTim();   // CS0234
      // try the following line instead
      // System.DateTime x = new System.DateTime();