Currently, I was trying to write an ASP.Net application that involved a user
clicking a ASP.Net button control
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<asp:Button ID="btnDownload"runat="server"Text="Download
File"OnClick="btnDownload_Click"/>
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Once the control is clicked the back end stores the users information (first
name, last name, email address, phone number, etc…) to a database. After that
information is stored to a database, the system would then allow the user to
download the file through an generic handler (.ashx file). The file size that
was to be downloaded is 600MB.
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protectedvoidbtnDownload_Click(objectsender,EventArgse)
{
connectionString=WebConfigurationManager.ConnectionStrings["connectionstring"].ConnectionString;
SqlConnection con=newSqlConnection(connectionString);
SqlCommand cmd=newSqlCommand("UserDownloadedFile",con);
cmd.CommandType=CommandType.StoredProcedure;
cmd.Parameters.Add(newSqlParameter("@Guid",SqlDbType.UniqueIdentifier));
cmd.Parameters["@Guid"].Value=newGuid(ViewState["Guid"].ToString());
try
{
introwsAffected;
rowsAffected=0;
con.Open();
rowsAffected=cmd.ExecuteNonQuery();
if(rowsAffected>0)
{
Response.Redirect("http://localhost/someWebApp/DownloadFile.ashx");
}
else
{
// Something went wrong.
}
}
catch(SqlException
exception)
{
// Log exception
}
finally
{
con.Close();
}
}
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Once the database is updated, I call the DownloadFile.ashx generic handler.
Upon execution of the generic handler I received the following
“OutOfMemoryException” error
This was a result from the following generic handler I was using
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<%@WebHandlerLanguage="C#"Class="DownloadFile"%>
usingSystem;
usingSystem.IO;
usingSystem.Web;
publicclassDownloadFile:IHttpHandler{
publicvoidProcessRequest(HttpContext context)
{
stringmediaName="myFile.zip";// 600MB in file
size
if(string.IsNullOrEmpty(mediaName))
{
return;
}
stringdestPath=context.Server.MapPath("~/Downloads/"+mediaName);
// Check to see if file exist
FileInfo fi=newFileInfo(destPath);
// If the file exist on the server then add it to the
database
if(fi.Exists)
{
HttpContext.Current.Response.ClearHeaders();
HttpContext.Current.Response.ClearContent();
HttpContext.Current.Response.AppendHeader("Content-Length",fi.Length.ToString());
HttpContext.Current.Response.ContentType="application/x-zip-compressed";
HttpContext.Current.Response.AppendHeader("Content-Disposition","attachment;
filename="+mediaName);
HttpContext.Current.Response.BinaryWrite(ReadByteArryFromFile(destPath));
HttpContext.Current.Response.End();
}
}
privatebyte[]ReadByteArryFromFile(stringdestPath)
{
byte[]buff=null;
FileStream fs=newFileStream(destPath,FileMode.Open,FileAccess.Read);
BinaryReader br=newBinaryReader(fs);
longnumBytes=newFileInfo(destPath).Length;
buff=br.ReadBytes((int)numBytes);
returnbuff;
}
publicboolIsReusable
{
get
{
returnfalse;
}
}
}
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This handler worked in the past, for very small files. The last time I was
using this the file size was about 300MB. My friend @homeraguas
reminded me that I might needed to check my web.config file to be sure that the
following maxRequestLength and executionTimeout was set. It wasn’t in the
web.config file. So I added the following
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<httpRuntime
maxRequestLength="600000"executionTimeout="7200"/>
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Recompiled and published, then gave it another go. Still, I came across the
“OutOfMemoryException” error. I looked around the net and came across this
blog’s article
utilizing the following method Reponse.TransmitFile();
The HttpReponse.TransmitFile()
method basically states it “Writes the specified file directly to an HTTP
response output stream without buffering it in memory.”
This makes sense to me, since the file I want to transfer is 600MB and I do
not think the current server I am writing this web application for does not have
adequate resources available. So the revision to the code I wrote/used is
as follows
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<%@WebHandlerLanguage="C#"Class="DownloadFile"%>
usingSystem;
usingSystem.IO;
usingSystem.Web;
publicclassDownloadFile:IHttpHandler{
publicvoidProcessRequest(HttpContext context)
{
stringmediaName="myFile.zip";// 600MB in file
size
if(string.IsNullOrEmpty(mediaName))
{
return;
}
stringdestPath=context.Server.MapPath("~/Downloads/"+mediaName);
// Check to see if file exist
FileInfo fi=newFileInfo(destPath);
try
{
if(fi.Exists)
{
HttpContext.Current.Response.ClearHeaders();
HttpContext.Current.Response.ClearContent();
HttpContext.Current.Response.AppendHeader("Content-Disposition","attachment;
filename="+fi.Name);
HttpContext.Current.Response.AppendHeader("Content-Length",fi.Length.ToString());
HttpContext.Current.Response.ContentType="application/octet-stream";
HttpContext.Current.Response.TransmitFile(fi.FullName);
HttpContext.Current.Response.Flush();
}
}
catch(Exception
exception)
{
HttpContext.Current.Response.ContentType="text/plain";
HttpContext.Current.Response.Write(exception.Message);
}
finally
{
HttpContext.Current.Response.End();
}
}
publicboolIsReusable
{
get
{
returnfalse;
}
}
}
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The result was that it worked.
What do you guys think? Is this an adequate solution? Have a good
one!
Downloading files from a server to client, using ASP.Net, when
file size is too big for MemoryStream using Generic Handlers (ashx),布布扣,bubuko.com
Downloading files from a server to client, using ASP.Net, when
file size is too big for MemoryStream using Generic Handlers (ashx)
