有滚动条的asp.net datagrid控件.txt

应客户要求再次开发有滚动条的ASP.Net DataGrid控件 从该例子中可以学习到对VS提供的标准控件进个性开发的思路

客户要一个有滚动条的ASP.Net DataGrid控件，只好写了：

using System;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.ComponentModel;

using System.Diagnostics;

using System.IO;

using System.Web.UI.Design.WebControls;

using System.Text;

using System.Drawing;

 

[assembly:TagPrefix("Microsoft.Gtec.Dsv", "gtecdsv")] 

namespace Microsoft.Gtec.Dsv

{

  /// <summary>

  /// Summary description for WebCustomControl1.

  /// </summary>

  [ToolboxData("<{0}:ScrollableFixedHeaderDataGrid runat=server></{0}:ScrollableFixedHeaderDataGrid>")]

  public class  ScrollableFixedHeaderDataGrid: System.Web.UI.WebControls.DataGrid

  {

    protected override void Render(HtmlTextWriter output)

    {

      //Use this flag to determine whether the component is in design-time or runtime.

      //The control will be rendered differently in IDE.

      //Don't bother to use DataGridDesigner.GetDesignTimeHtml

      bool designMode = ((Site != null) && (Site.DesignMode));

      //Backing up the properties need to change during the render process

      string tempLeft = Style["LEFT"];

      string tempTop = Style["TOP"];

      Unit tempHeight = Height;

      string tempTableStyle = Style["TABLE-LAYOUT"];

 

      //Render a "<div>" container with scrollbars.

      output.WriteBeginTag("div");

      output.WriteAttribute("id",ID + "_div");

      output.WriteAttribute("style",

        "HEIGHT: " + Height + ";" +

        //Leave 20px for the vertical scroll bar,

        //assuming the end-user will not set his scroll bar to more than 20px.

        "WIDTH: " + (Width.Value + 20) + "px;" + 

        "TOP: " + Style["TOP"] + ";" +

        "LEFT: " + Style["LEFT"] + ";" +

        "POSITION: " + Style["POSITION"] + ";" + 

        "OVERFLOW-X: auto;" +

        "Z-INDEX: " + Style["Z-INDEX"] + ";" +

        //Render the scrollbar differently for design-time and runtime.

        "OVERFLOW-Y: " + (designMode?"scroll":"auto")

        );

      output.Write(HtmlTextWriter.TagRightChar);

                        

      //The DataGrid is inside the "<div>" element, so place it at (0,0).

      Style["LEFT"] = "0px";

      Style["TOP"] = "0px";

      //Render the DataGrid.

      base.Render(output);

      output.WriteEndTag("div");

      //Restore the values

      Style["LEFT"] = tempLeft;

      Style["TOP"] = tempTop;

 

      //The following rendering is only necessary under runtime. It has negative impact during design time.

      if (!designMode) 

      {

        //Render another copy of the DataGrid with only headers.

        //Render it after the DataGrid with contents,

        //so that it is on the top. Z-INDEX is more complex here.

        //Set Height to 0, so that it will adjust on its own.

        Height = new Unit("0px");

        StringWriter sw = new StringWriter();

        HtmlTextWriter htw = new HtmlTextWriter(sw);

        //This style is important for matching column widths later.

        Style["TABLE-LAYOUT"] = "fixed";

        base.Render(htw);

        StringBuilder sbRenderedTable = sw.GetStringBuilder();

        htw.Close();

        sw.Close();

        Debug.Assert((sbRenderedTable.Length > 0),

          "Rendered HTML string is empty. Check viewstate usage and databinding.");

        string temp = sbRenderedTable.ToString();

        if (sbRenderedTable.Length > 0)

        {

          //AllowPaging at the top?

          if ((AllowPaging) && ((PagerPosition.Top == PagerStyle.Position || (PagerPosition.TopAndBottom == PagerStyle.Position)))) 

          {

            Trace.WriteLine(temp);

            sbRenderedTable.Replace(ID,ID + "_Pager", 0, (temp.IndexOf(ID) + ID.Length));

            temp = sbRenderedTable.ToString();

            string pager = temp.Substring(0, temp.ToLower().IndexOf(@"</tr>") + 5);

            Trace.WriteLine(pager);

            output.Write(pager);

            output.WriteEndTag("table");

            //Start of pager's <tr>

            int start = temp.ToLower().IndexOf(@"<tr");

            //End of pager's </tr>

            int end = temp.ToLower().IndexOf(@"</tr>") + 5;

            //Remove the <tr> for pager from the string. Prepare to render the headers.

            sbRenderedTable.Remove(start,end-start);

            Trace.WriteLine(sbRenderedTable.ToString());

            sbRenderedTable.Replace(ID + "_Pager",ID + "_Headers", 0, (temp.IndexOf(ID+"_Pager") + (ID+"_Pager").Length));

            temp = sbRenderedTable.ToString();

            string tableHeaders = temp.Substring(0, (temp.ToLower()).IndexOf(@"</tr>") + 5);

            Trace.WriteLine(tableHeaders);

            output.Write(tableHeaders);

            output.WriteEndTag("table");

            string headerID = ID + "_Headers";

            string pagerID = ID + "_Pager";

            string divID = ID + "_div";

            string adjustWidthScript = @"

                                                <script language=javascript>