string str1="Andreas Graßl";
string str2="Andreas Grassl";
Console.WriteLine(string.Equals(str1,str2)); //False
Console.WriteLine(string.Equals(str1,str2,StringComparison.CurrentCulture)); //True
So I suggest you change your code with string.Equals()
Details: http://msdn.microsoft.com/en-us/library/vstudio/cc165449.aspx