When you are reading "\u5b89\u5fbd\u5b5f\u5143" you get exactly what you read. The debugger escapes your strings before displaying them. The double backslashes in the string are actually single backslashes that have been escaped.
When you pass you hardcoded value, you are not actually passing in what you see on the screen. You are passing in four Unicode characters, since the C# string is unescaped by the compiler.
Darin already posted a way to unescape Unicode characters from the file, so I won't repeat it.
