string was not recognized as a valid dateTime.

Question

am using dateTimePicker in dataGridView and SQL database

private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
{
    try
    {
        string ColName = dataGridView1.Columns[e.ColumnIndex].Name;
        if (ColName == "ColEdit")
        {
            formExecutiveInfoEntry frm = new frmExecutiveInfoEntry(this);
            form.dtDateJoin.Text = dataGridView1.Columns[1].DefaultCellStyle.Format = "dd-MM-yyyy";
        }
    }
}