I'm getting the "missing a using directive or assembly reference" and no clue what's going wrong

Solution 1:

You probably don't have the System.Configuration dll added to the project references. It is not there by default, and you have to add it manually.

Right-click on the References and search for System.Configuration in the .net assemblies.

Check to see if it is in your references...

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Right-click and select Add Reference...

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Find System.Configuration in the list of .Net Assemblies, select it, and click Ok...

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The assembly should now appear in your references...

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Solution 2:

.Net framework of the referencing dll should be same as the .Net framework version of the Project in which dll is referred

Solution 3:

If you've tried the above solutions and haven't found the answer, make sure that the .NET versions of all projects are the same.

I ran into this problem when importing a .NET version 4.6.1 into a .NET version 4.6.2 project. Without any warnings from Visual Basic!

More Info: The type or namespace name could not be found