Please suggest which is the best to getting executing assembly location.
Assembly.GetAssembly(typeof(NUnitTestProject.RGUnitTests)).Location
It seems rather obvious: When you want the executing assembly, use GetExecutingAssembly.
GetExecutingAssembly
Sometimes you don't have one, for example when running as an Office add-in. You could use Assembly.GetAssembly instead.
Assembly.GetAssembly