How to fix binary search in winform C#

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C#

DataGridView

binary

My problem is, when I import a csv file to datagridview, then the binary search is working very well. For the second time as well. After the third time, the binary-search is not working well. It does not finds any object from the ArrayList.
I use Windows application for this project.

What I have tried:

Adding data to the ArrayList after csv is imported:

ListOfPeople.Add(Something.Trim());

Converting datagridview values to ArrayList before search in binary:

foreach (var row in dataGridView2.Rows.Cast<DataGridViewRow>())
{
    ListOfPeople[row.Index] = row.Cells[0].Value.ToString().Trim();
}

ListOfPeople is the ArrayList name.

Binary Search Code:

int index = this.ListOfPeople.BinarySearch(textBoxBinarySearch.Text);
if (index != -1)
{
        dataGridView2.SelectionMode = DataGridViewSelectionMode.RowHeaderSelect;
        dataGridView2.Rows[index].Selected = true;
        dataGridView2.CurrentCell = dataGridView2.Rows[index].Cells[0];
        MessageBox.Show("Index is equal to: " + index, "Binary Search");

        textBoxBinarySearch.Clear();
    }