Reading file content to string in .Net Compact Framework

StringBuilder sb = new StringBuilder();
using (StreamReader sr = new StreamReader("TestFile.txt")) 
{
    String line;
    // Read and display lines from the file until the end of 
    // the file is reached.
    while ((line = sr.ReadLine()) != null) 
    {
        sb.AppendLine(line);
    }
}
string allines = sb.ToString();