Check if string has bigger value

[deve]

I need to check for a string if it has bigger value then the one in text file .

My code is like this :

String vl = Scores();
if (string.IsNullOrEmpty(vl) == true)
{
string text = System.IO.File.ReadAllText(@"test.txt");
textBox3.Text = text;
VM = new VMessages("Wmedit//Edit");
VM.sendText(textBox3.Text);
VM.sendKey(Keys.Enter); 
}
else
{
System.IO.StreamWriter file = new System.IO.StreamWriter(@"test.txt");
file.WriteLine(vl);
file.Close();
string text = System.IO.File.ReadAllText(@"test.txt");
textBox3.Text = text;
VM = new VMessages("Wmedit//Edit");
VM.sendText(textBox3.Text);
VM.sendKey(Keys.Enter);
}
}

now it checks if it has zero value in the string, when it is 0 it reads from test.txt and sends it to the window. But I need is it has to check if it is 0 + if it is not 0 is it bigger value or not. If it is bigger then reads again from the test.txt .

How can I do this...

My string pharse code is like this:

try
{
String source = File.ReadAllText(textBox1.Text + @"\result.txt");
source = source.Replace("\r", "").Replace("\n", "");
GroupCollection[ ] gr = (from Match it in Regex.Matches(source, @"\s*1\.\s+""([^""]*)"" Name![^-]*Value \(([^\)]+)\)[^-]*Distance \: ([0-9\.]+) meters\s*", RegexOptions.IgnoreCase)
where it.Groups != null && it.Groups.Count == 4
select it.Groups).ToArray( );
if (gr == null || gr.Length == 0) { return null; }
Double max = (from GroupCollection it in gr select Convert.ToDouble(it[2].Value)).Max( );
String res = (from GroupCollection it in gr where Convert.ToDouble(it[2].Value) == max select it[-1] + "Congratulation : " + it[1] + " :::...Score...::: " + it[2] + " ...:::Distance Meters...::: " + it[3]).First();
return res;
}
catch
{
throw;
}
finally
{
} 
}

thanks..