Hello,

I to find code in vb but i can't convert it to c#:

Code:
              Dim Txt As String = ""
        For Each Nass As String In TextBox1.Text
            Nass = Regex.Replace(Nass, "[Aa]", "[Aa]")
            Nass = Regex.Replace(Nass, "[Bb]", "[Bb]")
            Nass = Regex.Replace(Nass, "[Cc]", "[Cc]")
            Nass = Regex.Replace(Nass, "[Dd]", "[Dd]")
            Nass &= "[ًٌٍَُِّْ]*"
            Txt &= Nass
        Next
I tried convert code by internet converter this result:

Code:
            string Txt = "";
            foreach (string Nass in txtBookTitle.Text)
            {
            Nass = Regex.Replace(Nass, "[Aa]", "[Aa]");
            Nass = Regex.Replace(Nass, "[Bb]", "[Bb]");
            Nass = Regex.Replace(Nass, "[Cc]", "[Cc]");
            Nass = Regex.Replace(Nass, "[Dd]", "[Dd]");
                Nass += "[ًٌٍَُِّْ]*";
                Txt += Nass;
            }
But get red line under Nass =

Please Help me
Thanks in advance