Question

我想通過處理程序在網格視圖中顯示圖像。但是當數據庫中沒有路徑時，它會顯示髒圖像標誌。我需要在沒有圖像的地方顯示「NOImage」圖像。

<asp:TemplateField HeaderText="Path_Image"> 
          <ItemTemplate> 
           <asp:Image ID="Image1" runat="server" ImageUrl='<%# "LargeImage.ashx?p=" + Eval("Name") + "&q=" + Eval("Vertual_Path") %>' /> 
          </ItemTemplate> 
</asp:TemplateField> 

///LargeImage.ashx ..

using System; 
using System.Drawing; 
using System.Drawing.Drawing2D; 
using System.Drawing.Imaging; 
using System.IO; 
using System.Text.RegularExpressions; 
using System.Web; 

public class LargeImage : IHttpHandler 
{ 
    private Regex _nameValidationExpression = new Regex(@"[^\w/]"); 
    private int _thumbnailSize = 250; 

    public void ProcessRequest(HttpContext context) 
    { 
     string photoName = context.Request.QueryString["p"]; 
     string P_Path = context.Request.QueryString["Q"]; 
     if (photoName == "") 
     { 
      //file = (byte[])reader["Image"]; 
      // FileStream fs = File.OpenRead(HttpContext.Current.Server.MapPath("~/Article/NoImage.png")); 
      //File = new byte[fs.Length]; 
      //fs.Read(File, 0, File.Length); 
      context.Server.MapPath("~/Article/NoImage.jpg"); 
     } 
     else 
     { 
      if (_nameValidationExpression.IsMatch(photoName)) 
      { 

       throw new HttpException(404, "Invalid photo name."); 
      } 
      string cachePath = Path.Combine(HttpRuntime.CodegenDir, photoName + ".Large.png"); 
      if (File.Exists(cachePath)) 
      { 
       OutputCacheResponse(context, File.GetLastWriteTime(cachePath)); 
       context.Response.WriteFile(cachePath); 
       return; 
      } 
      else 
      { 

      } 
      //string photoPath = context.Server.MapPath("~/Photo/" + photoName + ".jpg"); 
      // string photoPath = context.Server.MapPath("~/Photo/" + photoName + ".jpg"); 
      string photoPath = context.Server.MapPath(P_Path + "\\" + photoName + ".jpg"); 

      Bitmap photo; 
      try 
      { 
       photo = new Bitmap(photoPath); 
      } 
      catch (ArgumentException) 
      { 

       throw new HttpException(404, "Photo not found."); 
      } 
      context.Response.ContentType = "image/pjpeg"; 
      int width, height; 

      if (photo.Width > photo.Height) 
      { 
       width = _thumbnailSize; 
       height = photo.Height * _thumbnailSize/photo.Width; 
      } 
      else 
      { 
       width = photo.Width * _thumbnailSize/photo.Height; 
       height = _thumbnailSize; 
      } 
      Bitmap target = new Bitmap(width, height); 
      using (Graphics graphics = Graphics.FromImage(target)) 
      { 
       graphics.CompositingQuality = CompositingQuality.HighSpeed; 
       graphics.InterpolationMode = InterpolationMode.HighQualityBicubic; 
       graphics.CompositingMode = CompositingMode.SourceCopy; 
       graphics.DrawImage(photo, 0, 0, width, height); 
       using (MemoryStream memoryStream = new MemoryStream()) 
       { 

        //context.Response.AddHeader("Content-Disposition", "attachment; filename=\"" + photoName + "\""); 
        context.Response.AddHeader("Content-Disposition", "attachment; filename=\"" + DateTime.UtcNow.ToString() + "\""); 
        target.Save(memoryStream, ImageFormat.Jpeg); 
        // OutputCacheResponse(context, File.GetLastWriteTime(photoPath)); 
        // OutputCacheResponse(context, File.GetLastWriteTime(photoPath)); 
        using (FileStream diskCacheStream = new FileStream(cachePath, FileMode.CreateNew)) 
        { 
         memoryStream.WriteTo(diskCacheStream); 
        } 
        memoryStream.WriteTo(context.Response.OutputStream); 
        context.Response.Flush(); 
       } 
      } 
     } 
    } 

Answer 1

您可以使用此代碼嘗試 - 基於的ProcessRequest

public class ImageHandler : IHttpHandler 
{ 
public void ProcessRequest(System.Web.HttpContext ctx) 
{ 
     if(condition) // Adjust your condition 
     {  
     var path = ctx.Server.MapPath("~/images/NoImage.gif"); 
     var contentType = "image/gif"; 
     ctx.Response.ContentType = contentType; 
     ctx.Response.WriteFile (path); 
     } 

} 

public bool IsReusable { get {return true; } }   


} 

Answer 2

在頁面LargeImage.ashx，如果沒有記錄/圖像渲染，做一個重定向到你本地的靜態圖像（在你的圖片文件夾中說）。

這樣你就不依賴瀏覽器特定的「破碎」圖像。

如

Response.ContentType = "image/jpeg" 
Try 
    photo = GetPhoto(param) 
     IF photo is Nothing then 
      Response.Redirect("images/unknown.jpg", True) 
     Else 
      Response.Binarywrite(photo) 
     End if 
    Catch 
      Response.Redirect("images/unknown.gif", True) 
    Finally 
     photo.Dispose() 
    End Try 

Answer 3

在閱讀你的代碼，它看起來你的問題是HttpException（404， 「無效的圖片名稱。」 ）你在投擲。

瀏覽器會將其解釋爲破碎的圖像。

用重定向替換那些已知的本地圖像。