create string builder in a new class using c#

Question

can anybody tell me how to create a string builder in a new class (say v.cs) which is going to call into main  winform(form1.cs) project  using c# 

I have implemented below codes but it has working properly. I have  browsed for whole day but found nothing. So your single threads meant me lots

 

// codes for my new class say v.cs  

StringBuilder _sb= new StringBuilder();

public void v(StringBuilder sb)

{

sb.Replace("s", "A");

sb.Replace("hi","hello");   so on .... 

}

// codes for  form1.cs

private void button3_Click(object sender, EventArgs e)

{

StringBuilder sb= new StringBuilder(c1Editor1.Text);

v sb = new Jam(sb);

sb.display(); 

}

 

Thanks