It sounds like cbGrid.Text
is an empty string. If there is a missing operand, it's because it was not provided (it was blank).
A possible solution is to make sure to only run the filter if the value is not empty, or give it a default value.
private void txtGrid_TextChanged(object sender, EventArgs e)
{
if (!string.IsNullOrWhiteSpace(cbGrid.Text))
{
// only run when not empty
DataView dv = new DataView(dt);
dv.RowFilter = ""+cbGrid.Text + " like '%" + txtGrid.Text + "%'";
gridPlayers.DataSource = dv;
}
}