Need to "loop" these codes until all records be deleted...

Israel

Hi!

I have database with one column. I wrote these codes to make four important steps:

1. Loading records from database into combobox

2. Display always the first item into combobox after loading

3. Delete this first item after to be displayed

4. Refresh the combobox after delete a record

All these steps work very well with my codes. But I would like to do it repeatly until deleting the latest record without make a bug.

But this moment its gives this message on this line:

Additional information:Its not possible to modify a item colection when a DataSource property is defined.

This happen at this line:

this.comboBox1.Items.AddRange(list.ToArray());

private void button5_Click(object sender, EventArgs e)

{

Control p;

p = ((Button)sender).Parent;

p.SelectNextControl(ActiveControl, true, true, true, true);

int ia = 1;

conn.Open();

comm = new OleDbCommand("SELECT DISTINCT name FROM test1", conn);

OleDbDataReader sdr = comm.ExecuteReader();

DataTable dt = new DataTable();

dt.Load(sdr);

comboBox1.DisplayMember = "name";

comboBox1.DroppedDown = true;

List list = new List();

foreach (DataRow row in dt.Rows)

{

list.Add(row.Field("name"));

}

this.comboBox1.Items.AddRange(list.ToArray());//The bug its here

comboBox1.AutoCompleteMode = AutoCompleteMode.SuggestAppend;

comboBox1.AutoCompleteSource = AutoCompleteSource.ListItems;

conn.Close();

///////////////////////doesnt allow repeat item in combobox////////////

for (int i = 0; i < comboBox1.Items.Count; i++)

{

for (int y = 0; y < comboBox1.Items.Count; y++)

{

if (y != i && comboBox1.Items[i].ToString() == comboBox1.Items[y].ToString())

{

comboBox1.Items.RemoveAt(i);

break;

}

///////////////////////////////// Display First item

comboBox1.SelectedIndex = 0;

///////////////////////////////// Delete first item

String strConnection = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\Pario\Documents\Combobox_refresh\WindowsFormsApplication1\App_Datas\test.mdb;Persist Security Info=False";

string query = "delete from test1 where name='" + comboBox1.Text + "';";

OleDbConnection conDatabase = new OleDbConnection(strConnection);

OleDbCommand cmdDatabase = new OleDbCommand(query, conn);

OleDbDataReader myReader;

try

{

conn.Open();

myReader = cmdDatabase.ExecuteReader();

//MessageBox.Show("Dados excluidos com exito. Obrigado!");

while (myReader.Read())

{

}

catch (Exception ex)

{

MessageBox.Show(ex.Message);

}

finally

{

conn.Close();

}

///////////////////////////////// Refresh Database and Combobox

OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\Pario\Documents\Combobox_refresh\WindowsFormsApplication1\App_Datas\test.mdb;Persist Security Info=False");

con.Open();

OleDbCommand cmd = new OleDbCommand("select name from test1", con);

OleDbDataAdapter SDA = new OleDbDataAdapter();

SDA.SelectCommand = cmd;

DataTable DT = new DataTable();

SDA.Fill(DT);

comboBox1.DataSource = DT;

con.Close();

Application.DoEvents();

ia++;

int milliseconds = 2000;

Thread.Sleep(milliseconds);

button5.PerformClick(); //Trigger click event

}

5 Replies

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ali tuncer9y ago
Accepted answer
Looking at the code, I don't think you need "list" variable in button5_Click, just set dt as your combobox datasource..
Should be something like this :

conn.Open();
comm = new OleDbCommand("SELECT DISTINCT name FROM test1", conn);
OleDbDataReader sdr = comm.ExecuteReader();
DataTable dt = new DataTable();
dt.Load(sdr);
comboBox1.DisplayMember = "name";
comboBox1.DroppedDown = true;
comboBox1.DataSource = dt;
comboBox1.AutoCompleteMode = AutoCompleteMode.SuggestAppend;
comboBox1.AutoCompleteSource = AutoCompleteSource.ListItems;
conn.Close();

If you want to change(remove) items in combobox, you can't use comboBox1.Items.RemoveAt(i), you will get the same error, you need to make changes in datasource, which is dt..so you can remove it like dt.Rows.RemoveAt(i)..

Important thing is, once you set datasource to combobox, it doesn't let you make changes in the combobox items, you need to make changes in datasource..that's what Additional information:Its not possible to modify a item colection when a DataSource property is defined error means..
Israel9y ago
@ali tuncer Sorry, I would like to say its appear into combobox1 not label1.
ali tuncer9y ago
Where is label1? I don't see it in the code, I don't know what you are assigning to label..
Israel9y ago
@Ali tuncer

I do replace this code. Its works:
comboBox1.DataSource = list;

But the thing is when I click the button to run. Its works but showing me always this message on my label1: system.Data.DataRowView
Means that after each record is displayed this message appear on the label1.
ali tuncer9y ago
what happens when you set to datasource again in button5_Click?
instead of this this.comboBox1.Items.AddRange(list.ToArray());
try this : comboBox1.DataSource = list;