Does Scintilla need a directive? I keep getting an error?

So, when I drag in Scintilla to my C# form, and try to run it, I get the error:

The type or namespace name 'ScintillaNet' could not be found (are you missing a using directive or an assembly reference?)

The error appears to be coming from the designer for Form1.

I also get the warning (but not error):

The referenced assembly "ScintillaNet" could not be resolved beca开发者_开发问答use it has a dependency on "System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" which is not in the currently targeted framework ".NETFramework,Version=v4.0,Profile=Client". Please remove references to assemblies not in the targeted framework or consider retargeting your project.

So, I can't run my program...

What's wrong, and how do I fix it? I've installed scintilla just like how the directions for it suggested...

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I was also experiencing this error (although I am hosting in WPF not WinForms). It was caused by Visual Studio 2010 defaulting the project to .Net 4.0 Client profile rather than the full .Net 4.0 profile.