I created a helper function in my WP 7 project recently, to read a text file included in the project. You can try to use it, the function also working in WP 8 project :
public static class FileHelper
{
public static string ReadFile(string filePath)
{
var ResrouceStream = Application.GetResourceStream(new Uri(filePath, UriKind.Relative));
if (ResrouceStream != null)
{
Stream myFileStream = ResrouceStream.Stream;
if (myFileStream.CanRead)
{
StreamReader myStreamReader = new StreamReader(myFileStream);
return myStreamReader.ReadToEnd();
}
}
return "";
}
}
Then I can use that function this way (in this example the file resides under Assets folder) :
var textFileContent = FileHelper.ReadFile(@"Assets\MyTextFile.txt");