Overview: I have a Windows Form application, built in .Net 4.7.2 using Visual Studio 2019. The form has 3 PartID combo boxes, allowing the user to select 3 distinct part IDs from a finite list of parts in the drop down.
Problem: When the combo box was being filled with values in the drop down list, the following exception was thrown.
Exception:
System.AccessViolationException
HResult=0x80004003
Message=Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
Source=<Cannot evaluate the exception source>
StackTrace:
<Cannot evaluate the exception stack trace>
Code:
private void cbPO_LostFocus(object sender, EventArgs e)
{
FillPartID1(poLines);
}
private void cbPO_SelectedIndexChanged(object sender, EventArgs e)
{
FillPartID1(poLines);
}
private void FillPartID1(DataTable poLines)
{
AutoCompleteStringCollection acs1 = new AutoCompleteStringCollection();
foreach (var rec in poLines.AsEnumerable())
acs1.Add(rec.ItemArray[1].ToString());
cbPartID1.AutoCompleteCustomSource = acs1;
cbPartID1.AutoCompleteMode = AutoCompleteMode.SuggestAppend; //Exception thrown here during 2nd execution
cbPartID1.AutoCompleteSource = AutoCompleteSource.CustomSource;
cbPartID1.DataSource = poLines;
cbPartID1.DisplayMember = "PART_ID";
cbPartID1.ValueMember = "PART_ID";
cbPartID1.SelectedIndex = -1;
}
Cause: The FillPartID1() was being called twice due to event handlers cbPO_SelectedIndexChanged() and cbPO_LostFocus().
Solution: Refactor the code so FillPartID1() is called only once.
