Steps to make assembly strong name(SN) to DLL:
Open .net command prompt.
Go to the folder contanig DLL.
Type sn -k test.snk, you can use any file name instead of test. This will create test .snk file in that folder.
Open the assemblyinfo.cs file of project.
Type file path in this tag [assembly:AssemblyKeyFile@"E:\hemant\practice\HP\bin\Debug\HP.snk")]
Build the applications, [...]