我试图在我的新类中使用dll导入，但是在这个声明类型中获取错误属性'DllImport'是无效的

The error Attribute 'DllImport' is not valid on this declaration type. It is only valid on 'method' declarations. Tried to add the dll import before the class in a method but same error.The error Attribute 'DllImport' is not valid on