doubt in adding data in database in c#

Question

Hi... I am new in C#. I am doing a billing project. I have one doubt. In my form i have text box. for sales entry. when i enter in that text box it have to be added to my database in the field of sales. For example in my database for an item pen it already have sales value 5 in database. if i enter again 5 in text box my database value should be 10. I don't know what to do... so please help me

Biswa Pujarini Mohapatra · Answer

ASpx.cs protected void Button1_Click(object sender EventArgs e) { string connectionString = Persist Security Info=False;User ID=sa;Password=123;Initial Catalog=SalesDB;//TODO change your connection string using (SqlConnection con = new SqlConnection(connectionString)) { string SqlQuery =; SqlCommand cmd = new SqlCommand(Insert into table (sale) values(SUM(@sale)) con);//To DO change your table and columna name con.Open(); if (con.State == ConnectionState.Open) { cmd.Parameters.Add(@sale SqlDbType.Int).Value = txtSales.Text; try { cmd.ExecuteNonQuery(); con.Close(); } catch(SqlException ex) { throw ex; } } }