Thread Performance

[C# Programming]

Hi All,

Im hoping someone can give me an idea on what I may be doing wrong (if anything). In my project I have a Combo Box which I populate from a SQL Database (using a Dataset and a for statement looping through each record). I have done it on form load and it works well however I decided to run it from a background thread so I become familiar with threads and for a few other reasons.

Anyway, i have done it using a Thread but I seem to have taken a very large performance hit. Without a thread, populating the combo box (on Form_Load) it takes about 1 second. With the Thread it takes about 6 seconds.

Im assuming since Im new with threads there is something obvious in my code that is wrong. Here is the relevant code in question:-

//Create Delegates for the Threads to Access The Forms UI
private delegate void UpdateComboBox(ComboBox cboName,string strItemToAdd);

Code in the Form_load Event
//Hide the Status Label
lblStatus.Visible = false;

//Start by Enabling the Loading Circle
//This is an indicator that the Background Thread is still running
//The Background thread is connecting to the database and populating the Combo Boxes
lblLoadingFormData.Text = "Loading Data";
lblLoadingFormData.Visible = true;
lcFormData.Active = true;

//Create the Thread which will Update the Combo Boxes
Thread thrPopulateComboBoxes = new Thread(this.PopulateComboBoxes);
thrPopulateComboBoxes.Start();

Code to Populate the Combo Box

private void PopulateComboBoxes()
{
//This Method will Populate the ComboBoxes on the Form
//Customers

ArrayList al = new ArrayList();

//Customers Combo Box
al = myDatabaseFunctions.PopulateComboBox("SELECT Name FROM tblCustomers ORDER BY Name ASC", "Name", "Customers");

foreach (string s in al)
{
this.Invoke(new UpdateComboBox(this.AddItemToComboBox),new object[] {cboCustomer,s.ToString()});
}
}

I know the issue is not with the Arraylist as this is the same sort of code I am using in a non thread and the performance is fine

Finally the code to add to Combo Box

private void AddItemToComboBox(ComboBox cboName, string strItem)
{
cboName.Items.Add(strItem);
}

Can any1 offer some thoughts as to why Im taking such a performance hit? Am I doing something wrong with the threads?

Thanks in advance,

Daniel.