Cuando la celda del cuadro desplegable DataGridView es incorrecta, cambie el color de fondo como un indicador

        ///  <summary> 
        /// cell font color
         ///  </ summary> 
        Color cellForeColor = Color.Black;
         ///  <summary> 
        /// cell background normal color
         ///  </ summary> 
        Color cellNomalColor = Color.white;
         ///  <summary> 
        /// error color de fondo de células
         ///  </ resumen> 
        color = cellErrorColor Color.Red;
         ///  <summary> 
        /// células edición
         ///  </ resumen> 
        ///  <param name = "remitente"> </ param> 
        ///  <param name = "e "> </param> 
        privado void dgvSnpDistribute_EditingControlShowing ( remitente de objeto , DataGridViewEditingControlShowingEventArgs e) 
        { 
            ComboBox cb = e.Control como ComboBox;
            // if (cbox! = null &&! object.ReferenceEquals (cbox, cb) && cb! = null || cbox == null)
             // {
             //     cbox = cb;
            // } 
            if (cb! = null ) 
            { 
                cb.DropDownStyle = ComboBoxStyle.DropDownList; 
                cb.DrawMode = DrawMode.OwnerDrawFixed; 
                cb.DrawItem - =Cb_DrawItem; 
                cb.DrawItem + = Cb_DrawItem; 
            } 
        } 

        ///  <summary> 
        /// 单元 格 重绘
         ///  </summary> 
        ///  <param name = "sender"> </param> 
        ///  <param name = "e"> </ param> 
        private  void Cb_DrawItem ( remitente del objeto , DrawItemEventArgs e) 
        { 
            if (e.Index < 0 ) 
            { 
                return ; 
            } 

            ComboBox cb = remitente como ComboBox;
            si (cb! ) 
            { 
                cb.BackColor = cellNomalColor;
                valor de cadena = cb.Items [e.Index] .ToString ();
                using (Brush foreBrush = new SolidBrush (cellForeColor))
                 using (Brush backBrush = new SolidBrush (cb.BackColor)) 
                { 
                    e.Graphics.FillRectangle (backBrush, e.Bounds); 
                    e.DrawBackground (); 
                    e.DrawFocusRectangle (); 
                    e.Graphics.DrawString (value, cb.Font, foreBrush, e.Bounds); 
                } 
            } 
        } 

        ///  <summary> 
        /// 重新 编写 单元 格 绘制 函数
         ///  </summary> 
        ///  <param name = "sender"> </param> 
        ///  <param name = "e" > </param> 
        private  void dgvSnpDistribute_CellPainting ( remitente de objeto , DataGridViewCellPaintingEventArgs e) 
        { 
            if (e.ColumnIndex < 0 || e.RowIndex < 0 ) 
            { 
                return ; = dgvSnpDistribute.Rows [e.RowIndex] .Cells [e.ColumnIndex] como DataGridViewComboBoxCell;
            if (cell! = null ) 
            { 
                e.Paint (e.ClipBounds, DataGridViewPaintParts.Border);
                e.Paint (e.ClipBounds, DataGridViewPaintParts.ContentBackground); 

                usando (Brush foreBrush = new SolidBrush (cellForeColor))
                 usando (Brush backBrush = new SolidBrush (cell.Style.BackColor))
                 usando (StringFormat format = new StringFormat ()) 
                { 
                    Rectangle rect = new Rectangle (e.CellBounds.X + 1 , e.CellBounds.Y + 1, e.CellBounds.Width - 19 , e.CellBounds.Height - 3 ); 
                    format.LineAlignment =StringAlignment.Center; 
                    e.Graphics.FillRectangle (backBrush, rect); 
                    e.Graphics.DrawString (cell.FormattedValue.ToString (), e.CellStyle.Font, foreBrush, rect, format); 
                } 

                e.Paint (e.ClipBounds, DataGridViewPaintParts.ErrorIcon); 
                e.Paint (e.ClipBounds, DataGridViewPaintParts.Focus); 
                e.Handled = verdadero ; 
            } 
        }

En la condición incorrecta, cambie el color de fondo de cell.Style.BackColor