I am building a library software and I need some help from you. In the book lending section, I have a text box for typing the book number and a combo for the book name. The system is such that when I type the book's id in the text box, it comes up with its name in the combo box, like searching in the data grid view. The problem is that I do not know how to code the database and call and in general it is better to say I do not know what to do! Please help.

CodePudding user response：

If you want the combobox to display the book name according to the Id you enter in the textbox, you can refer to the following code：

string connStr = " Your own database connect string ";
string sql = "select Name from Book where Id=@id";//Your own sql query statement
    private void textBox1_TextChanged(object sender, EventArgs e)
    {
        comboBox1.Items.Clear();
        SqlConnection conn = new SqlConnection(connStr);
        using (conn)
        {
            SqlParameter parm = new SqlParameter("@id", Convert.ToInt32(textBox1.Text));
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = sql;
            cmd.Connection = conn;
            cmd.Parameters.Add(parm);
            conn.Open();
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    comboBox1.Text = dr.GetValue(0).ToString();
                }
            }
            else
            {
                MessageBox.Show("Please enter correct ID");
            }
        }
    }