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Question

I wants do this.uploaded file is source file.please help me

            String A = textBox1.Text.Trim();

            A = A.Replace("ab", "cdq");
            A = A.Replace("ef", "ghe");
            A = A.Replace("ij", "klt");
            A = A.Replace("mn", "opf");
            A = A.Replace("qu", "rsg");
            A = A.Replace("tu", "vwd");

            textBox2.Text = (A);

if i select "ab" from textbox1,highlight "cdq" in textbox2
if i select "ef" from textbox1,highlight "ghe" in textbox2
if i select "ij" from textbox1,highlight "klt" in textbox2