如何使用FileStream启动另存为对话框

Question

My project is a Sharepoint Web-App, and it will generate a text file for the user and offer it for the user to download.

The web-app generates a string value and should use FileStream to create a text file out of it. The user clicks a button and they should get a save-as dialogue.

Now, it is simple enough to use FileStream to write to the user's local drive, but how do you prompt them for the location and THEN save it there ?

There are lots of questions about how to write to the local disk, and there are questions about how to open the save-dialogue in the browser. But I have not found any that answer the question of using the two methods together.

To write the file, we can use this :

        using (var fs = new FileStream(@"C:\test.txt", FileMode.Create, FileAccess.ReadWrite)) {
            TextWriter tw = new StreamWriter(fs);
            tw.Write("Hello World");
            tw.Flush();
        }

and to open the save-as dialog, we can do this , which will tell the browser a file is ready for downloading which will open the browser's own save dialogue:

            if (resp.IsClientConnected) {
                resp.Clear();
                resp.ClearHeaders();
                //Indicate the type of data being sent
                resp.ContentType = "text/plain";    //".htm", "html" = "text/html"
                resp.AppendHeader("Content-Disposition", "attachment; filename=\"" + Path.GetFileName(gentextfilename) + "\"");
                resp.AppendHeader("Content-Length", reader.BaseStream.Length.ToString());
                resp.TransmitFile(file_name); //does not buffer into memory, therefore scales better for large files and heavy usage
                resp.End();
            }

Now, is there a way to combine these? I don't want to save the file to the server and then download it. I want to save it directly to a save location specified by the user. And to make all of this worse, it's a Sharepoint web-app, so it will run inside of Sharepoint, so I don't think you can use the folderBrowserDialog1 or SaveFileDialog method l ike you can in a desktop application .

Summary of What Answer is Being Sought:

How can I create a file (without creating one on the server) to save to download location of the user's choice?

Answer 1

No, there is no way to do that directly as you are used to in Windows desktop development. This is the nature of the protocol used.

You can't use the desktop file dialogs from within your ASP.NET application to ask the user where to save things. You have to rely on the browser to do so.

The best option you have is what you already show: content disposition. Give the browser as much information as you can and let the user decide what to do with it.

If you can use ASP.NET MVC, you can take advantage of the streamed responses, like FileStreamResult or using standard ASP.NET, using CopyTo .