probleme avec apostrophe '

UPDATE myTable SET champ1 ='val1' WHERE id=condtion

string sql = "Select * from matable where categorie = @CategoryName"

  categoriesAdapter.SelectCommand.Parameters.Add(

    "@CategoryName", SqlDbType.VarChar, 80).Value = "toasters";

UPDATE myTable SET champ1 ='val1' WHERE id=condtion

UPDATE myTable SET champ1 ='l'activité' WHERE id=condtion

public string RempApos(string str) 

{

     return str.Replace("'", "''");

}



private void button1_Click(object sender, EventArgs e)

{

    textBox2.Text = "UPDATE myTable SET champ1 = '" + RempApos(textBox1.Text) + "' WHERE id = condtion" ;

}