Ok, maybe not quite ONE line. This will do the trick:
$0$0
$0
$0(requires LINQ)$0
$0$0
$0
$0System.Security.Cryptography.MD5.Create()$0
$0.ComputeHash(Encoding.Default.GetBytes(tohash))$0
$0.Select(x => x.ToString("x2"))$0
$0.Aggregate(new System.Text.StringBuilder(), (acc, x) => acc.Append(x))$0
$0.ToString();$0
$0
$0