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Download the Solution Example:

Solution file: ComboBoxFromTable.dbsln
Database file: ComboBoxFromTable.db

  • Solution Name: Combo Box From Table
  • Software Version: v10
  • Keywords: Displays. ComboBox. Datasets.

Summary

This solution demonstrates how to populate ComboBoxes using a data table.

Technical Information

First, you need to obtain control of the ComboBox on the display. This is achieved through the following lines:


ComboBox cbxListCodes;

public void DisplayOpening()
{
    cbxListCodes = CurrentDisplay.GetControl("cbxListCodes") as ComboBox;
}


After that, you need to load your data table. In this example, we will retrieve the entire table asynchronously.


// Selects the whole table
@Dataset.Table.Products.WhereCondition = "";
DataTable dt = await @Dataset.Table.Products.SelectCommandAsync();


Next, you can use a simple foreach loop to select which rows to add to the ComboBox, as shown in the code snippet below.

// Inserts each row to the combobox
foreach (DataRow row in dt.Rows)
{
    cbxListCodes.Items.Add(row["ListCode"]);
}


Now, using an EventHandler, you can determine the value selected by the client from the ComboBox and update the other TextBoxes accordingly but this time, we'll use a different method to also retrieve the status of the SelectCommand, enabling easier troubleshooting if any issues occur. To achieve this, we'll create a new variable, "status," which will be passed by reference. This way, we'll change the SelectCommand method to SelectCommandWithStatusAsync.

Finally, we retrieve the status value using a tag, allowing us to monitor the status directly in the property watch.

cbxListCodes.SelectionChanged += new SelectionChangedEventHandler(codeChanged);

public void codeChanged(object sender, SelectionChangedEventArgs args)
{
if(cbxListCodes.SelectedValue == null)
return;

    // Selecting from the DB only the Item corresponding to the Code Selected in the ComboBox
    // Due to dealing with async methods that can't have multiple outputs
	// it's used a workaround by passing a reference to an int.
    // Therefore, we use this reference to be an input for our SelectCommandWithStatusAsync() method
    // and retrieve its value by getting the Value property.

TRef<int> status = new TRef<int>(); 
@Dataset.Table.Products.WhereCondition = "ListCode = " + cbxListCodes.SelectedValue.ToString(); 	if(@Dataset.Table.Products.SelectCommandWithStatusAsync(status).IsCompleted) 
	{
		@Tag.Status = status.Value;
	} 
}

Reference Information

→ See Displays (Desktop and Web) for more information.

→ See ComboBox Control for more information.

→ See Datasets Tables for more information.

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