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Dynamic in the immediate window causes 'Microsoft.CSharp.RuntimeBinder.Binder' is not defined or imported error

Posted by: admin November 29, 2017 Leave a comment


If I use dynamic in the immediate window of Visual Studio I get an error

Predefined type ‘Microsoft.CSharp.RuntimeBinder.Binder’ is not defined or imported

How can I fix that?


You should add reference to Microsoft.CSharp library in the selected project or in the startup project. And your project should reference .NET Framework 4 or higher.

MSDN about immediate window context:

When establishing the context for design time expression evaluation,
Visual Studio references the currently selected project in Solution
Explorer. If no project is selected in Solution Explorer, Visual
Studio attempts to evaluate the function against the startup project.
If the function cannot be evaluated in the current context, you will
receive an error message.


Two things are important. Check the following:

  1. That your project properties are referencing .NET Framework 4 or higher (if that is not the case, change it: Right click on the project, select the “Properties…” menu item, then select as target framework “.NET Framework 4” (or higher))
  2. That you have added the “Microsoft.CSharp” assembly as reference (note that step 1., which requires to re-load the project, must be done before you can do that)

Afterwards you can use the dynamic type. The reference needs to be added in the selected project or in the startup project in order to become available in the immediate window’s scope.

  1. Go to project->add reference.
  2. select assemblies from the side bar and Framework
  3. check Microsoft.CSharp

Happy coding!


Namespace: Microsoft.CSharp.RuntimeBinder

Assembly: Microsoft.CSharp (in Microsoft.CSharp.dll)