Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

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 2^nd 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.