C＃更新数据库中listBox中的每个项目

Question

I have created a Database that has an ID column (aitisi_ID) and a category column(kat_aitisis). I want to Update the kat_aitisis column for every ID that shows up on my listBox with the string kat1 .

Edit 2: the column 'aitisi_ID' is int

I have this so far,but it doesnt work (cn is my SqlConnection and cmd is SqlCommand):

// Edit: This is the code that I use to add Items to my listBox
private void loadlist()
    {
        listBox1.Items.Clear();
        listBox2.Items.Clear();
        cn.Open();
        string kat = "Εγκυρη";
        cmd.CommandText = ("SELECT aitisi_ID,moria FROM Table2 WHERE kat_aitisis='"+kat+"' ORDER BY moria DESC");
        dr = cmd.ExecuteReader();
        if (dr.HasRows)
        {
            while (dr.Read())
            {
                listBox1.Items.Add(dr[0].ToString());
                listBox2.Items.Add(dr[1].ToString());
            }
        }
        cn.Close();
    }


string kat1 = "aaaaa";

        cn.Open();
        for (int i = 0; i < listBox1.Items.Count; i++)
        {

            listBox1.SetSelected(i, true);
            cmd.CommandText = "UPDATE Table2 SET kat_aitisis='"+kat1+"' WHERE aitisi_ID='"+listBox1.SelectedIndex+"'";
            cmd.ExecuteNonQuery();
            cmd.Clone();

        }  
        cn.Close();

Answer 1

If the column 'aitisi_ID' is of numeric type the correct update query is

    string kat1 = "aaaaa";
    cmd.CommandText = "UPDATE Table2 SET kat_aitisis=@kat WHERE aitisi_ID=@id";
    cmd.Parameters.AddWithValue("@kat", kat1);
    cmd.Parameters.AddWithValue("@id", 0);
    cn.Open();
    for (int i = 0; i < listBox1.Items.Count; i++)
    {
        cmd.Parameters["@id"].Value = Convert.ToInt32(listBox1.Items[i]));
        cmd.ExecuteNonQuery();
    }  
    cn.Close();

Created a parameterized query with two params and set with initial values.
One parameter of type string with an invarian value (kat1) The second parameter is of integer type with a dummy initial value.
Then, in the loop only the varying parameter (@id) will be updated.
The value for the second parameter is taken from the Item collection of ListBox1 that is filled with integers (all the items are passed to the update value) and converted back to int as expected by the datatable

Answer 2

You don't need to wrap the Id in a single quote block. Since it is an integer, SQL server will be happy with WHERE aitisi_ID='"+listBox1.SelectedIndex+"', but you do need to ToString() it.

WHERE aitisi_ID="+listBox1.SelectedIndex.ToString()+"

Answer 3

Also try creating code less general, with a foreach :

    foreach(object i in listBox1.Items)

You don't need single quotes for integers, just for strings. Try to post your error, debug result, try to put breakpoints and give more info please.