在DataGrid中添加一个LookUpColumn,以比较灵活地实现DictValue值代替DictID值显示.

 在一个项目中,我遇到这样一个问题: 数据库字段只存储了一个字典ID1,在DataGrid中显示时,需要用相应的字典Value1来代替字典ID1显示.解决这个问题一般有两个方法:
方法1:  数据库查询Sql脚本直接把相应的字典Value1值查询出来.
方法2: 在显示DataGrid时,把相应的字典ID1转换成字典Value1显示.

关于方法1, 实现相对简单但是不灵活,并且我们采用的是强类型的DataSet,不想经常修改强类型Dataset的定义
关于方法2, 实现上相对复杂一些但是比较灵活,也不用破坏已定义的强类型DataSet.

于是我就决定采用方法二,上网也找了不少资料,终于在codeproejct找到一篇比较符合我需求的文章,我的实现逻辑如下:在创建Datagrid的column时,对于需要替换的column:Dict1用自定义的LookUpColumn来代替, 设置LookupColumn的Datasource DispalyMember及ValueMember,当Dataset中相应字段的值与LookupColumn的Datasource的ValueMember值相匹配时,显示相应的DispalyMember值.具体代码如下:

   DataGridLookupColumn lcolumnex = new DataGridLookupColumn(); 
   lcolumnex.MappingName = "Dict1"; 
   lcolumnex.HeaderText = lcolumnex.MappingName;   
   lcolumnex.comboBox.ValueMember = "DictID"; 
   lcolumnex.comboBox.DisplayMember = "DictValue"; 
   lcolumnex.Width = 80; 
   lcolumnex.comboBox.DataSource = CommonValue.GetDictList();//返回Dict结构(有DictID,DictValue属性)组成的一个ArrayList 
   lTableStyle.GridColumnStyles.Add(lcolumnex); 

具体的DataGridLookupColumn类实现代码如下:

/**//*本代码原稿由http://www.codeproject.com/cs/miscctrl/RenDataGridComboBoxColumn.asp获取,并做了相应的改动 by Zendyhu
*/
DataGridLookupColumn#region DataGridLookupColumn
    //**********************************************************************************************
    //    DataGridLookupColumn
    //**********************************************************************************************
    public class DataGridLookupColumn : DataGridColumnStyle 
    { //DataGridLookupColumn {
        private    DataGridComboBox    combobox;
        private    bool                    edit;

        //-------------------------------------------------------------------------------------------
        //    Constructors and destructors
        //-------------------------------------------------------------------------------------------
        public DataGridLookupColumn() 
        {
            combobox                                        = new DataGridComboBox();
            combobox.Visible                            = false;
            combobox.DropDownStyle                    = ComboBoxStyle.DropDownList;
            combobox.Leave                                += new EventHandler(ComboHide);
            combobox.SelectionChangeCommitted    += new EventHandler(ComboStartEditing);
            edit                                            = false;
        } // DataGridLookupColumn

        //-------------------------------------------------------------------------------------------
        //    Properties
        //-------------------------------------------------------------------------------------------
        public ComboBox comboBox 
        {
            get 
            {
                return combobox;
            }
        } // comboBox

        //-------------------------------------------------------------------------------------------
        //    ComboBox event handlers
        //-------------------------------------------------------------------------------------------
        private void ComboHide(object sender, EventArgs e) 
        {
            // When the ComboBox looses focus, then simply hide it.
            combobox.Hide();
        } // ComboHide

        private void ComboStartEditing(object sender, EventArgs e) 
        {
            // Enter edit mode.
            edit = true;
            base.ColumnStartedEditing((Control)sender);
        } // ComboStartEditing

        //-------------------------------------------------------------------------------------------
        //    Override DataGridColumnStyle
        //-------------------------------------------------------------------------------------------
        protected override void SetDataGridInColumn(DataGrid value) 
        {
            // Add the ComboBox to the DataGrids controls collection.
            // This ensures correct DataGrid scrolling.
            value.Controls.Add(combobox);
            base.SetDataGridInColumn(value);
        } // SetDataGridInColumn

        protected override void Abort(int rowNum) 
        {
            // Abort edit mode, discard changes and hide the ComboBox.
            edit = false;
            Invalidate();
            combobox.Hide();
        } // Abort

        protected override void Edit(System.Windows.Forms.CurrencyManager source, int rowNum, System.Drawing.Rectangle bounds, bool readOnly, string instantText, bool cellIsVisible) 
        {
            // Setup the ComboBox for action.
            // This includes positioning the ComboBox and showing it.
            // Also select the correct item in the ComboBox before it is shown.
            combobox.Parent            = this.DataGridTableStyle.DataGrid;
            combobox.Bounds            = bounds;
            combobox.Size                = new Size(this.Width, this.comboBox.Height);
            comboBox.SelectedValue    = base.GetColumnValueAtRow(source, rowNum).ToString();
            combobox.Visible            = (cellIsVisible == true) && (readOnly == false);
            combobox.BringToFront();
            combobox.Focus();    
        } // Edit

        protected override bool Commit(System.Windows.Forms.CurrencyManager source, int rowNum) 
        {
            // Commit the selected value from the ComboBox to the DataGrid.
            if (edit == true) 
            {
                edit = false;
                this.SetColumnValueAtRow(source, rowNum, combobox.SelectedValue);
            }

            return true;
        } // Commit

        protected override object GetColumnValueAtRow(System.Windows.Forms.CurrencyManager source, int rowNum) 
        {
            // Return the display text associated with the data, insted of the
            // data from the DataGrid datasource.
            return combobox.GetDisplayText(base.GetColumnValueAtRow(source, rowNum));
        } // GetColumnValueAtRow

        protected override void SetColumnValueAtRow(CurrencyManager source, int rowNum, object value) 
        {
            // Save the data (value) to the DataGrid datasource.
            // I try a few different types, because I often uses GUIDs as keys in my
            // data.

            // String.
            try 
            {
                base.SetColumnValueAtRow(source, rowNum, value.ToString());
                return;
            } 
            catch {}

            // Guid.
            try 
            {
                base.SetColumnValueAtRow(source, rowNum, new Guid(value.ToString()));
                return;
            } 
            catch {}

            // Object (default).
            base.SetColumnValueAtRow(source, rowNum, value);
        } // SetColumnValueAtRow

        protected override int GetMinimumHeight() 
        {
            // Return the ComboBox preferred height, plus a few pixels.
            return combobox.PreferredHeight;
        } // GetMinimumHeight
        
        protected override int GetPreferredHeight(Graphics g, object val) 
        {
            // Return the font height, plus a few pixels.
            return FontHeight + 2;
        } // GetPreferredHeight

        protected override Size GetPreferredSize(Graphics g, object val) 
        {
            // Return the preferred width.
            // Iterate through all display texts in the dropdown, and measure each
            // text width.
            int        widest        = 0;
            SizeF        stringSize    = new SizeF(0, 0);
            foreach (string text in combobox.GetDisplayText()) 
            {
                stringSize    = g.MeasureString(text, base.DataGridTableStyle.DataGrid.Font);
                if (stringSize.Width > widest) 
                {
                    widest = (int)Math.Ceiling(stringSize.Width);
                }
            }

            return new Size(widest + 25, combobox.PreferredHeight + 2);
        } // GetPreferredSize

        protected override void Paint(Graphics g, Rectangle bounds, CurrencyManager source, int rowNum) 
        {
            Paint(g, bounds, source, rowNum, false);
        } // Paint

        protected override void Paint(Graphics g, Rectangle bounds, CurrencyManager source, int rowNum, bool alignToRight) 
        {
            string            text                = GetColumnValueAtRow(source, rowNum).ToString();
            Brush                backBrush        = new SolidBrush(base.DataGridTableStyle.BackColor);
            Brush                foreBrush        = new SolidBrush(base.DataGridTableStyle.ForeColor);
            Rectangle        rect                = bounds;
            StringFormat    format            = new StringFormat();

            // Handle that the row can be selected.
            if (base.DataGridTableStyle.DataGrid.IsSelected(rowNum) == true) 
            {
                backBrush        = new SolidBrush(base.DataGridTableStyle.SelectionBackColor);
                foreBrush        = new SolidBrush(base.DataGridTableStyle.SelectionForeColor);
            }

            // Handle align to right.
            if (alignToRight == true) 
            {
                format.FormatFlags    = StringFormatFlags.DirectionRightToLeft;
            }

            // Handle alignment.
            switch (this.Alignment) 
            {
                case HorizontalAlignment.Left:
                    format.Alignment    = StringAlignment.Near;
                    break;
                case HorizontalAlignment.Right:
                    format.Alignment    = StringAlignment.Far;
                    break;
                case HorizontalAlignment.Center:
                    format.Alignment    = StringAlignment.Center;
                    break;
            }

            // Paint.
            format.FormatFlags        = StringFormatFlags.NoWrap;
            g.FillRectangle(backBrush, rect);
            rect.Offset(0, 2);
            rect.Height -= 2;
            g.DrawString(text, this.DataGridTableStyle.DataGrid.Font, foreBrush, rect, format);
            format.Dispose();
        } // PaintText

    } // DataGridLookupColumn
    #endregion

    DataGridComboBox#region DataGridComboBox
    //**********************************************************************************************
    //    DataGridComboBox
    //**********************************************************************************************
    public class DataGridComboBox : ComboBox 
    {
        private const int WM_KEYUP = 0x101;

        protected override void WndProc(ref System.Windows.Forms.Message message) 
        {
            // Ignore keyup to avoid problem with tabbing and dropdown list.
            if (message.Msg == WM_KEYUP) 
            {
                return;
            }

            base.WndProc(ref message);
        } // WndProc

        public string GetValueText(int index) 
        {
            // Validate the index.
            if ((index < 0) && (index >= base.Items.Count))
                throw new IndexOutOfRangeException("Invalid index.");

            // Get the text.
            string    text            = string.Empty;
            int        memIndex        = -1;
            try 
            {
                base.BeginUpdate();
                memIndex                    = base.SelectedIndex;
                base.SelectedIndex    = index;
                text                        = base.SelectedValue.ToString();
                base.SelectedIndex    = memIndex;
            } 
            catch 
            {
            } 
            finally 
            {
                base.EndUpdate();
            }

            return text;
        } // GetValueText

        public string GetDisplayText(int index) 
        {
            // Validate the index.
            if ((index < 0) && (index >= base.Items.Count))
                throw new IndexOutOfRangeException("Invalid index.");

            // Get the text.
            string    text            = string.Empty;
            int        memIndex        = -1;
            try 
            {
                base.BeginUpdate();
                memIndex                    = base.SelectedIndex;
                base.SelectedIndex    = index;
                text                        = base.SelectedItem.ToString();
                base.SelectedIndex    = memIndex;
            } 
            catch 
            {
            } 
            finally 
            {
                base.EndUpdate();
            }

            return text;
        } // GetDisplayText

        public string GetDisplayText(object value) 
        {    //mdified by zendyhu 2004-12  to fixed bug when the getValueByID
            string text1 = this.ValueMember;
            if (text1.Equals(string.Empty))
                return "";

            if (DataSource == null)
                return "";
            if (!(DataSource is IList))
            {
                return "";
            }

            foreach(object obj in (IList)DataSource)
            {
                object obj2 = FilterItemOnProperty(obj,text1);

                if(value.ToString().Trim().ToUpper() == obj2.ToString().Trim().ToUpper())
                {
                    return GetItemText(obj);
                }
            }
            return "";
            // Get the text.
//            string    text            = string.Empty;
//            int        memIndex        = -1;
//            try 
//            {                
//                base.BeginUpdate();
//                memIndex                    = base.SelectedIndex;
//                base.SelectedValue    = value;
//                text                        = base.Text.ToString();
//                base.SelectedIndex    = memIndex;
//            } 
//            catch 
//            {
//            } 
//            finally 
//            {
//                base.EndUpdate();
//            }
//
//            return text;
        } // GetDisplayText

        public string[] GetDisplayText() 
        {
            // Get the text.
            string[]    text            = new string[base.Items.Count];
            int        memIndex        = -1;
            try 
            {
                base.BeginUpdate();
                memIndex                    = base.SelectedIndex;
                for (int index = 0; index < base.Items.Count; index++) 
                {
                    base.SelectedIndex    = index;
                    text[index]                = base.SelectedItem.ToString();
                }
                base.SelectedIndex    = memIndex;
            } 
            catch 
            {
            } 
            finally 
            {
                base.EndUpdate();
            }

            return text;
        } // GetDisplayText

    } // DataGridComboBox
    #endregion