我想通过输入要加载的值的特定ID将数据库中的值加载到文本框中

Question

I want to load the values from my database by typing the ID that I want to load, example is library, I want to load the values of Book Id #2 to the textbox the code works, but it only displays the last values in the database or the last row, it doesn't follow the book id that I typed

ex. Book 1 = Harry Potter, JK Rowling. Book 2 = Dictionary, Unknown. Book 3 = Science, Unknown.

Load book id 1, but the results are Science, Unknown.

Here's the code

try
{
    con.Open();

    adp = new SqlDataAdapter("SELECT COUNT(*) FROM Bookinfo WHERE BookNumber='" + textBox3.Text + "'", con);
    dt = new DataTable(); 
    adp.Fill(dt);

    if (dt.Rows[0][0].ToString() == "1")
    {
        cmd2 = new SqlCommand("SELECT * FROM Bookinfo WHERE BookNumber = '" + textBox3.Text + "';", con);

        using (SqlDataReader read = cmd.ExecuteReader())
        {
            while (read.Read())
            {
                textBox4.Text = (read["DateReceive"].ToString());
                textBox5.Text = (read["Class"].ToString());
                textBox6.Text = (read["Author"].ToString());
                textBox7.Text = (read["BookName"].ToString());
                textBox8.Text = (read["Edition"].ToString());
                textBox9.Text = (read["Volume"].ToString());
                textBox10.Text = (read["Pages"].ToString());
                textBox11.Text = (read["Source"].ToString());
                textBox12.Text = (read["Price"].ToString());
                textBox13.Text = (read["Publisher"].ToString());
                textBox14.Text = (read["Year"].ToString());
                textBox15.Text = (read["Remarks"].ToString());
            }
        }

        con.Close();

        MessageBox.Show("Book Loaded");
    }
    else
    {
        MessageBox.Show("Book doesn't exist");
        con.Close();
    }
}
catch (Exception ex)
{
    MessageBox.Show(ex.Message, "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Warning);
};

Thank you

Answer 1

You are filling the text boxes from a SqlReader attached to a SqlCommand called cmd. However, the shown SqlCommand is cmd2. You are not showing what you think you are.

Also get rid of the while (read.Read), you are just setting the same boxes again and again.

Another thing: When you use ADO directly, there is so much boilerplater code you have to write, I recommend using something like Dapper, which takes a lot of the tedious work away.

And as BWA said: Never concatenate Sql. Use parameters to avoid Sql-injection.