Hi fuatse,
It is because that the UserControl designer donot add aUserControl.Load event for this data source. You need add the event manually for your customized UserControl. Try something like the following.
private void DataUc_Load(object sender, EventArgs e)
{
this.testTableAdapter.Fill(this.dataSet1.test);//use your own TableAdapter and DataSet
}
Hope this helps.
Regards.