I am currently moving code from my app_code folder to a class library. I have tagged several methods with [System.Web.Script.Serialization.ScriptIgnore] attributes. My class library cannot see this namespace. My add references dialog cannot see this namespace. How do I properly use this tag from a class library?
Here is the error: The type or namespace name 'ScriptIgnoreAttribute' could not be found (are you missing a using directive or an assembly reference?)
The ScriptIgnoreAttribute class is in the System.Web.Extensions.dll assembly (Located under Assemblies > Framework in the VS Reference Manager). You have to add a reference to that assembly in your class library project.
You can find this information at top of the MSDN page for the ScriptIgnoreAttribute class.
You need to add a reference to System.Web.Extensions.dll in project for System.Web.Script.Serialization error.
来源：https://stackoverflow.com/questions/1156313/adding-system-web-script-reference-in-class-library