"the name "lr_load_dll" does not exist in the current context"

Hi everybody,

I try  to load our C# based dll to test the functions inside the dll. but I get problem when I use the statement: 

namespace Script
{
    public partial class VuserClass
    {
        public int vuser_init()
        {
            lr_load_dll(" C:\\PerfApp\\VELinkedServiceTestInterface_19_11_1111\\bin\\ValidationEngine.LinkedServices.Client.dll ");
            return 0;
        }
    }
}

The compile is filed with following error message:

 "the name "lr_load_dll" does not exist in the current context" 

Any idea why?