the complete version
private void button1_Click (object sender, EventArgs e)
System.IO.StreamReader sr = new
System.IO.StreamReader(openFileDialog1.FileName);
private void button2_Click (object sender, EventArgs e)
String find textbox1.Text
string replace = "dog";
File.writeAllText(openFileDialog1.FileName,File.ReadAllText(openFileDialog1.FileName).Replace(find, replace));
also need to add a textbox
solved Replacing a word in a txt using c# in visual studios