How to: Use an Assembly from the Web in Visual Studio
This topic shows how to use an assembly that you download from the Web in Visual Studio. For security reasons, Visual Studio blocks you from loading a Web assembly in the Choose Items and Add Reference dialog boxes.
Unblocking an assembly that is downloaded from the Web gives it Full Trust. Only unblock assemblies that you trust.
To unblock a Web assembly
Close Visual Studio.
Using Windows Explorer, browse to the assembly that you downloaded from the Web.
Right-click the assembly, and from the shortcut menu, select Properties.
The Properties dialog box opens.
On the General tab, click the Unblock button to indicate that this assembly is trusted
The Unblock button will not appear if the assembly is already unblocked and available.
Click OK to close the Properties dialog box.
Restart Visual Studio and open your project.
You should now be able to browse to the assembly in the Choose Items or Add Reference dialog boxes.