I want to add the value in a textbox to a column in db called Quantity by using Update, so every time i click save will collection that in db (Quantity)
I'm sorry my English not good

note: db=invoice , Table=Product
Edit: solve it , i hope this code will be usefull for ppl

```
         private void button1_Click(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection("Data Source=NAWAF;Initial Catalog=invoice;Integrated Security=True");

        con.Open();
        SqlCommand cmd = new SqlCommand(@"INSERT INTO [invoice].[dbo].[invoice]
            ([Invoice_Number]
            ,[Inventory_ID]
            ,[Received_Date]
            ,[Supplier_Code]
            ,[Supplier_Name]
            ,[Product_Code]
            ,[Product_name]
            ,[Serial_Number]
            ,[MGF_Date]
            ,[Product_unit]
            ,[ReceivedQ])
       VALUES     
            ('" + textBox1.Text + "' ,'" + comboBox1.Text + "' , '" + textBox3.Text + "' , '" + comboBox2.Text + "' , '" + comboBox3.Text + "' , '" + comboBox4.Text + "' , '" + comboBox5.Text + "' , '" + textBox2.Text + "' , '" + textBox4.Text + "' , '" + comboBox6.Text + "' , '" + textBox6.Text + "')", con);

               cmd.ExecuteNonQuery();

               con.Close();
               con.Open();
               SqlDataAdapter sda = new SqlDataAdapter("Select Invoice_Number,Received_Date,Supplier_Code,Supplier_Name,Product_Code,Product_name,Serial_Number,MGF_Date,ReceivedQ from invoice where   Invoice_Number like '" + textBox1.Text + "'", con);
               DataTable dt = new DataTable();
               sda.Fill(dt);
               dataGridView1.DataSource = dt;
              SqlCommand ccm= new SqlCommand("UPDATE product SET quantity += '" + textBox6.Text + "' FROM product WHERE Product_name like '" + comboBox5.Text + "'", con);
               ccm.ExecuteNonQuery();
               textBox3.Text = "";
               textBox2.Text = "";
               textBox4.Text = "";
               comboBox4.Text = "";
               comboBox5.Text = "";
               comboBox6.Text = "";
               textBox6.Text = "";
               con.Close();

    }

```