Наличие картинки на другом сайте.

using System.Net;
using System.IO;

private void button1_Click(object sender, EventArgs e) {
    try {
        WebRequest request = WebRequest.Create(@"http://virtuality.bv.du/hc.avatar");
        WebResponse response = request.GetResponse();
        if (response.ContentType == @"image/jpeg") {
            using (Graphics gfx = this.CreateGraphics())
            using (Image img = Image.FromStream(response.GetResponseStream())) {
                gfx.DrawImage(img, new Point(10, 10));
                gfx.Flush();
            }
        }
    } catch (WebException webException) {
        MessageBox.Show(webException.Message);
    }
}

Dim wrRequest As WebRequest
                            wrPCRequest = WebRequest.Create("http://www.yyy.m/images/IconsCatalog/" & .Item("Code").ToString.Trim & ".jpg")
                            Dim wrResponse As WebResponse
                            wrResponse = wrRequest.GetResponse()

using System;
using System.Data;
using System.Configuration;
using System.IO;
using System.Net;
using System.Web;
using System.Web.Caching;

public class ImageProxy : IHttpHandler {

    private static string RemoteImageDirectory = @"http://www.remotehost.com/pictures/";

    private static string DefaultImageFile = @"~/images/default.jpg";

    private static TimeSpan CacheDuration = new TimeSpan(0, 5, 0); // 5 minutes

    private static int MaxCachableImageSize = 51200; // 50 kbytes

    public void ProcessRequest(HttpContext context) {
        context.Response.ContentType = @"image/jpeg";
        byte[] imageBuffer = null;
        string image = (context.Request.Params["img"] ?? "");
        if (image != "") {
            imageBuffer = GetRemoteImage(context, image);
        } else {
            imageBuffer = GetDefaultImage(context);        
        }
        context.Response.BinaryWrite(imageBuffer);
    }

    private byte[] GetDefaultImage(HttpContext context) {
        FileInfo defaultImage = new FileInfo(context.Server.MapPath(DefaultImageFile));
        using (FileStream stream = defaultImage.OpenRead()) {
            byte[] imageBuffer = new byte[defaultImage.Length];
            stream.Read(imageBuffer, 0, imageBuffer.Length);
            return imageBuffer;
        }
    }

    private void CacheRemoteImage(HttpContext context, string remoteImageUrl, byte[] image) {
        if(image.Length < MaxCachableImageSize)
            context.Cache.Add(remoteImageUrl, image, null, DateTime.Now + CacheDuration, Cache.NoSlidingExpiration, CacheItemPriority.Default, null);
    }

    private byte[] GetRemoteImage(HttpContext context, string imageName) {
        byte[] imageBuffer = null;
        string remoteImageUrl = RemoteImageDirectory + imageName;
        object cachedImage = context.Cache[remoteImageUrl];
        if (cachedImage != null) {
            imageBuffer = (byte[]) cachedImage;
        } else {
            try {
                WebRequest request = WebRequest.Create(remoteImageUrl);
                WebResponse response = request.GetResponse();
                if (response.ContentType == @"image/jpeg") {
                    using (Stream stream = response.GetResponseStream()) {
                        imageBuffer = new byte[response.ContentLength];
                        stream.Read(imageBuffer, 0, imageBuffer.Length);
                    }
                } else {
                    imageBuffer = GetDefaultImage(context);
                }
            } catch {
                imageBuffer = GetDefaultImage(context);
            }
            CacheRemoteImage(context, remoteImageUrl, imageBuffer);
        }
        return imageBuffer;
    }
   
    public bool IsReusable {
        get {
            return true;
        }
    }
}

<system.web>
        <httpHandlers>
            <add type="ImageProxy" verb="GET" path="imageproxy"/>
        </httpHandlers>
    </system.web>

http://www.myhost.com/imageproxy
http://www.myhost.com/imageproxy?img=remoteimage.jpg

<img src="~/imageproxy?img=put_filename_here.img" />

<%@ WebHandler Language="VB" Class="ImageProxy" %>
Public Class ImageProxy : Implements IHttpHandler
    Private Shared RemoteImageDirectory As String = "http://www.xxx.com/"
    Private Shared DefaultImageFile As String
    Private Shared CacheDuration As TimeSpan = New TimeSpan(0, 1, 0) ' 1 minutes
    Private Shared MaxCachableImageSize As Integer = 51200
    '--------------------------------------------------------------------------------------------------------
    Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
        Get
            Return True
        End Get
    End Property
    '--------------------------------------------------------------------------------------------------------
    Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
        context.Response.ContentType = "image/jpeg"
        Dim imageBuffer() As Byte = Nothing
        Dim image As String
        image = context.Request.Params("img")
        DefaultImageFile = context.Request.Params("def")
        If (image <> "") Then
            imageBuffer = GetRemoteImage(context, image)
        Else
            imageBuffer = GetDefaultImage(context)
        End If
        context.Response.BinaryWrite(imageBuffer)
    End Sub
    '--------------------------------------------------------------------------------------------------------
    Private Function GetDefaultImage(ByVal context As HttpContext) As Byte()
        Dim defaultImage As FileInfo = New FileInfo(context.Server.MapPath(DefaultImageFile))
        Dim stream As FileStream = defaultImage.OpenRead
        Dim imageBuffer() As Byte = New Byte((defaultImage.Length) - 1) {}
        stream.Read(imageBuffer, 0, imageBuffer.Length)
        Return imageBuffer
    End Function
    '--------------------------------------------------------------------------------------------------------
    Private Sub CacheRemoteImage(ByVal context As HttpContext, ByVal remoteImageUrl As String, ByVal image() As Byte)
        If (image.Length < MaxCachableImageSize) Then
            context.Cache.Add(remoteImageUrl, image, Nothing, (DateTime.Now + CacheDuration), Cache.NoSlidingExpiration, CacheItemPriority.Default, Nothing)
        End If
    End Sub
    '--------------------------------------------------------------------------------------------------------
    Private Function GetRemoteImage(ByVal context As HttpContext, ByVal imageName As String) As Byte()
        Dim imageBuffer() As Byte = Nothing
        Dim remoteImageUrl As String = (RemoteImageDirectory + imageName)
        Dim cachedImage As Object = context.Cache(remoteImageUrl)
        If (Not (cachedImage) Is Nothing) Then
            imageBuffer = CType(cachedImage, Byte())
        Else
            Try
                Dim request As WebRequest = WebRequest.Create(remoteImageUrl)
                Dim response As WebResponse = request.GetResponse
                If (response.ContentType = "image/jpeg") Then
                    Dim stream As Stream = response.GetResponseStream
                    imageBuffer = New Byte((response.ContentLength) - 1) {}
                    stream.Read(imageBuffer, 0, imageBuffer.Length)
                Else
                    imageBuffer = GetDefaultImage(context)
                End If
            Catch ex As System.Exception
                imageBuffer = GetDefaultImage(context)
            End Try
            CacheRemoteImage(context, remoteImageUrl, imageBuffer)
        End If
        Return imageBuffer
    End Function
End Class

Try
    Dim request As WebRequest = WebRequest.Create(remoteImageUrl)
    Dim response As WebResponse = request.GetResponse
    Try
        If (response.ContentType = "image/jpeg") Then
            Dim stream As Stream = response.GetResponseStream
            Try
                imageBuffer = New Byte((response.ContentLength) - 1) {}
                stream.Read(imageBuffer, 0, imageBuffer.Length)
            Finally
                [COLOR="Red"]stream.Close[/COLOR]
            End
        Else
            imageBuffer = GetDefaultImage(context)
        End If
    Finally
        [COLOR="Red"]response.Close[/COLOR]
    End
Catch ex As System.Exception
    imageBuffer = GetDefaultImage(context)
End Try

<%@ WebHandler Language="VB" Class="ImageProxy" %>
Public Class ImageProxy : Implements IHttpHandler
    Private Shared RemoteImageDirectory As String = "http://www.xxx.com"
    Private Shared DefaultImageFile As String = "img/NoPict/130X130.gif"
    Private Shared CacheDuration As TimeSpan = New TimeSpan(0, 10, 0) ' 10 minutes
    Private Shared MaxCachableImageSize As Integer = 51200 * 100
    '--------------------------------------------------------------------------------------------------------
    Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
        Get
            Return True
        End Get
    End Property
    '--------------------------------------------------------------------------------------------------------
    Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
        context.Response.ContentType = "image/jpeg"
        Dim imageBuffer() As Byte = Nothing
        Dim image As String
        image = context.Request.Params("img")
        If (image <> "") Then
            imageBuffer = GetRemoteImage(context, image)
        Else
            imageBuffer = GetDefaultImage(context)
        End If
        context.Response.BinaryWrite(imageBuffer)
    End Sub
    '--------------------------------------------------------------------------------------------------------
    Private Function GetDefaultImage(ByVal context As HttpContext) As Byte()
        Dim defaultImage As FileInfo = New FileInfo(context.Server.MapPath(DefaultImageFile))
        Dim stream As FileStream = defaultImage.OpenRead
        Dim imageBuffer() As Byte = New Byte((defaultImage.Length) - 1) {}
        stream.Read(imageBuffer, 0, imageBuffer.Length)
        Return imageBuffer
    End Function
    '--------------------------------------------------------------------------------------------------------
    Private Sub CacheRemoteImage(ByVal context As HttpContext, ByVal remoteImageUrl As String, ByVal image() As Byte)
        If (image.Length < MaxCachableImageSize) Then
            context.Cache.Add(remoteImageUrl, image, Nothing, (DateTime.Now + CacheDuration), Cache.NoSlidingExpiration, CacheItemPriority.Default, Nothing)
        End If
    End Sub
    '--------------------------------------------------------------------------------------------------------
    Private Function GetRemoteImage(ByVal context As HttpContext, ByVal imageName As String) As Byte()
        Dim imageBuffer() As Byte = Nothing
        Dim remoteImageUrl As String = (RemoteImageDirectory + imageName)
        Dim cachedImage As Object = context.Cache(remoteImageUrl)
        If (Not (cachedImage) Is Nothing) Then
            imageBuffer = CType(cachedImage, Byte())
        Else
            Try
                Dim request As WebRequest = WebRequest.Create(remoteImageUrl)
                Dim response As WebResponse = request.GetResponse
                Try
                    If (response.ContentType = "image/jpeg") Then
                        Dim stream As Stream = response.GetResponseStream
                        Try
                            imageBuffer = New Byte((response.ContentLength) - 1) {}
                            stream.Read(imageBuffer, 0, imageBuffer.Length)
                        Finally
                            stream.Close()
                        End Try
                    Else
                        imageBuffer = GetDefaultImage(context)
                    End If
                Finally
                    response.Close()
                End Try
            Catch ex As System.Exception
                imageBuffer = GetDefaultImage(context)
            End Try
            CacheRemoteImage(context, remoteImageUrl, imageBuffer)
        End If
        Return imageBuffer
    End Function
End Class