ASP.Net: Download files from server with their original name

Introduction :

Purpose of writing this post is to share a way to resolve a very common but important issue with uploading-downloading file in ASP.Net. I don’t claim it to be the most efficient way but it works for me.

Problem:

While uploading a file to the server we may save it with its original file name and may code like-

FileUploader1.SaveAs(Server.MapPath("UploadedFiles/" + FileUploader1.FileName));

But, problem is if we upload another file with same name as previous file then the previous one will be replaced with the latest one. Now all the links for downloading both theses files will reference to the same file on the server.
Again we may resolve this issue by saving files with unique name on the server and may code like-

FileUploader1.SaveAs(Server.MapPath("UploadedFiles/" + DateTime.Now.ToString("yyyyMMddhhmmssfffffff") + System.IO.Path.GetExtension(FileUploader1.FileName);));

By doing this we will lose the original file name forever. But, in some or, more scenarios user may expect the file to be downloaded to his/her hard-disk with the original file name with which he/she uploaded the file to the server. (Example: Uploading-Downloading multiple resumes of a candidate).

We can solve this issue by storing both the names of a file i,e original & unique name on server.

The actual headache now comes in to picture. File is saved on the server with some unique name but we want the to change it’s name to the original name while user downloading it to his/her hard-disk.

Solution:

[View Demo]

The above said problem can be solved by following few steps. For the illustration I am taking a Gridview to show files for downloading and LinkButton for the download links.

• Store both actual and unique names of the file in Database
• Use a Hidden Field to store actual(unique) file name in the gridview

  <asp:TemplateField HeaderText="Uploaded File">
   <ItemTemplate>
   <asp:LinkButton ID="lnkDownload" Text='<%#Eval("FileNameOriginal")%>' runat="server" OnClick="lnkDownload_Click" />
   <asp:HiddenField ID="hfDownload" runat="server" Value='<%#Eval("FileNameActual")%>' />
   </ItemTemplate>
   </asp:TemplateField>
  
  

• Now, put following code in the link button click event

  LinkButton lnkDwnload = (LinkButton)sender;
   GridViewRow grow = (GridViewRow)lnkDwnload.Parent.Parent;
   HiddenField hfDownload = (HiddenField)grow.FindControl("hfDownload");
   Response.AddHeader("Content-Disposition", "attachment;filename=" + lnkDwnload.Text);
   Response.ContentType = GetContentType(Server.MapPath("~/UploadedFiles/" + hfDownload.Value.ToString()));
   Response.TransmitFile(Server.MapPath("~/UploadedFiles/" + hfDownload.Value.ToString()));
   Response.End();
  
  

Note that I have used a method GetContentType() to get the content type/MIME type of the file to be downloaded.

private string GetContentType(string fileName)
 {
 string contentType = "application/octetstream";
 string ext = System.IO.Path.GetExtension(fileName).ToLower();
 Microsoft.Win32.RegistryKey registryKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(ext);
 if (registryKey != null && registryKey.GetValue("Content Type") != null)
 contentType = registryKey.GetValue("Content Type").ToString();
 return contentType;
 }

Note : Microsoft.Win32 is OS specific MSDN

For a universal solution we may use another way of getting the MIME type.

private string GetContentType(string fileName)
 {
 string ext = System.IO.Path.GetExtension(fileName).ToLower();
 switch (fileName)
 {

//add as many extensions of file types you expect to be uploaded

//for a complete list you may visit http://stackoverflow.com/questions/1029740/get-a-mime-from-an-extension

case ".doc": return "application/msword";

case ".docx": return "application/vnd.openxmlformats-officedocument.wordprocessingml.document";

case ".jpeg": return "image/jpeg";

case ".jpg": return "image/jpeg";

case ".bmp": return "image/bmp";

default: return "application/octet-stream";

}
}

Conclusion:

This works very fine for me. If you are facing problem then drop a comment, it will be my pleasure to help you. Any better idea is welcome.

Thanks for reading !

C Sharp: Find greater of two numbers

Assumption:

int num1 =double.Parse(Console.ReadLine());
int num2 = double.Parse(Console.ReadLine());

Supplied numbers are not equal.

Way 1:(Using Relational operator)

if (num1 > num2)
    Console.WriteLine("Max is:{0}", num1);
else
    Console.WriteLine("Max is:{0}", num2);

Way 2:(Using Conditional operator)

Console.WriteLine("Max is:{0}", num1>num2?num1:num2);

Way 3:(Using Math.Max())

Console.WriteLine("Max is:{0}", Math.Max(num1,num2));

Way 4:(Using Math.Abs())

Console.WriteLine("Max is:{0}", ((num1+num2)+Math.Abs(num1-num2))/2);

Analysis:
Among these ways I don’t think the first three solutions need any explaination. But what we will anayse here is the Way 4. The half of the summation of sum of two numbers and their absolute difference results the greater of the two. Similarly we can get the lower among them as the half of the substraction between the sum of the two numbers and their absolute difference.
Ex:

Console.WriteLine("Min is:{0}", ((num1+num2)-Math.Abs(num1-num2))/2);