exception while accessin dll's

Question

Here is the Code i have in my application :

try
{
Assembly assemblyInstance =
Assembly.LoadFrom(@"C:\Data\Dlls\Myfunctions.dll") ;
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}

when i'm trying to load the dll i'm getting an exception -----

Could not load file or assembly ' C:\Data\Dlls\Myfunctions.dll' or one of
its dependencies. The module was expected to contain an assembly manifest.

what is the problem????????