Please Can Someone Point Out Whats Wrong With My Code

Hi,
I have code on a page to update one table and insert info into another, but I cant make it work. I am new to coding and i think there are many mistakes. Please can someone pick out a few that need to be changed for the page to work.
Code:
private bool ExecuteUpdate(int quantity)
{
  SqlConnection con = new SqlConnection();
  con.ConnectionString = "ConnectionString";

  con.Open();

  SqlCommand command = new SqlCommand();
  command.Connection = con;
  TextBox TextBox1 = (TextBox)FormView1.FindControl("TextBox1");
  Label labname = (Label)FormView1.FindControl("Label3");
  Label labid = (Label)FormView1.FindControl("Label13");
               
        command.CommandText = "UPDATE Items SET Quantityavailable WHERE productID='@productID'  = " + TextBox1.Text +

 command.ExecuteNonQuery();
        return true;
  con.Close();
}


    private bool ExecuteInsert(String quantity)
    {
        SqlConnection con = new SqlConnection();
        con.ConnectionString = "ConnectionString";

        con.Open();

        SqlCommand command = new SqlCommand();
        command.Connection = con;
        TextBox TextBox1 = (TextBox)FormView1.FindControl("TextBox1");
        Label labname = (Label)FormView1.FindControl("Label3");
        Label labid = (Label)FormView1.FindControl("Label13");

        command.CommandText = "INSERT Transactions SET Usersname = @UserName" +
          "; INSERT Transactions SET Itemid WHERE productID='@productID' = @productID; INSERT Transactions SET itemname = @Itemsname" +
          "; INSERT Transactions SET Date WHERE productID='@productID' = " + DateTime.Now.ToString() +
          "; INSERT Transactions SET Qty WHERE productID='@productID' = " + TextBox1.Text;
        command.Parameters.Add("@UserName", System.Web.HttpContext.Current.User.Identity.Name);
        command.Parameters.Add("@Itemsname", labname.Text);
        command.Parameters.Add("@productID", labid.Text);
        command.ExecuteNonQuery();
        return true;
        con.Close();
    }





protected void Button2_Click(object sender, EventArgs e)
{
  TextBox TextBox1 = FormView1.FindControl("TextBox1") as TextBox;
  ExecuteUpdate(Int32.Parse(TextBox1.Text) );
  ExecuteInsert(Int32.Parse);
}
 
Current error message is:
The best overloaded method match for 'detailproview.ExecuteInsert(string)' has some invalid arguments
to Line 74: ExecuteInsert(Int32.Parse); Thanks if someone can help!Jon