ASP.NET C#OutofMemoryException大文件上载

public class FileUploader : IHttpHandler
{
 public void ProcessRequest(HttpContext context)
 {
    HttpRequest request = context.Request;

    context.Response.ContentType = "text/html";
    context.Response.ContentEncoding = System.Text.Encoding.UTF8;
    context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
    var tempPath = request.PhysicalApplicationPath + "FilesTempFiles";        
    byte[] buffer = new byte[request.ContentLength];
    using (BinaryReader br = new BinaryReader(request.InputStream))
    {
        br.Read(buffer,buffer.Length);
    }
    var tempName = WriteTempFile(buffer,tempPath);
    context.Response.Write("{"success":true}");
    context.Response.End();
 }

 public bool IsReusable
 {
    get { return true; }
 }

 private string WriteTempFile(byte[] buffer,string tempPath)
 {
    var fileName = GetUniqueFileName(tempPath);
    File.WriteAllBytes(tempPath + fileName,buffer);
    return fileName;
 }
 private string GetUniqueFileName(string tempPath)
 {
    var guid = Guid.NewGuid().ToString().ToUpper();
    while (File.Exists(tempPath + guid))
    {
        guid = Guid.NewGuid().ToString().ToUpper();
    }
    return guid;
 }
}

当我上传大文件时,这会导致OutOfMemoryException.有人能说出使用这样的处理程序上传大文件的正确方法吗？