ASP.NET interview questions: – Show us how to restrict users to upload a specified file extension in ASP.NET?

This is not one of the typical .NET interview questions but on knowledge aspect you will find this as interesting because while you are working in some of the IT company or project this situation can occur in front of you so at that time this might help you in some extent.

So let’s see a small and simple example to understand it in better manner.

In order to see it practically just follow the following steps.

Step1: – create a new project of ASP.NET for that just go to >> File
>> New >> Project >> Web >> select ASP.NET Empty Web
Application.

Step2: – now, just simply add a Web form page in to your application for that just go to >> Solution Explorer >> Right click on the project name >> Add >> New Item >> Select Web Form.

Step3: – Now Add a FileUpload control and Button control
from the ToolBox to the WebForm.aspx Page.

The WebForm.aspx page should appear like below diagram.

Step4: – Now simply just add the below code snippet in to
WebForm1.aspx.cs
file.

protected void Button1_Click(object sender, EventArgs e)
{
if ((FileUpload1.PostedFile != null) && (FileUpload1.PostedFile.ContentLength > 0))
{
string filename = System.IO.Path.GetFileName(FileUpload1.PostedFile.FileName);
// The below line of code with take the extension of the selected file by the user.
string extension = System.IO.Path.GetExtension(FileUpload1.PostedFile.FileName);

// The below line of code is the location where the file will be saved.
string location = Server.MapPath("UploadedFiles")+"\\"+filename;

// The below “if” condition will see the whether the file is .docx 
or not and according to that the condition statement will execute.

if (extension == ".docx")
{
try
{
FileUpload1.PostedFile.SaveAs(location);
Label2.Text = "The File has been successfully uploaded";
}
catch (Exception ex)
{
Label2.Text = "Error : " + ex.Message.ToString();
}
}
else
{
Label2.Text = "Please Select a .docx file only";
}
}
else
{
Label2.Text = "Please Enter a File";
}
}

The above code snippet is for the Button control for uploading the
selected file to the server and with the extension condition.

Once you have completed all the above steps just run your application to get a resultant result.

The above diagram is the running page that we have created.

Now, let’s first select a different extension file and see that the file is
successfully added to the server or not.

Once you have selected the file now just click on the upload button.

As we have not selected the specified file extension, we expect that the file should not be saved and an error of block statement should get executed like below diagram.

The above diagram proves the point that the user can only select the specified file extension.

Now, let us select a .docx file as we have specified in the code of statement and see that it is getting saved to the server or not.

Now, just click the upload button to upload the selected file to the server and if everything goes right you will see the result like below diagram.

See the following video on Authentication and Authorization: –


Get more learning materials for ASP.NET interview questions

Regards,

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About c# and .NET Interview questions

This blog is for developers who want to crack .NET and C# interviews. It has all tips and tricks needed to crack .NET interviews , C# interview , SQL Server interview , Java interview , WCF Interview , Silverlight interview , WPF interview , LINQ interview , Entity framework Interview. Do not forget to watch our Learn step by step video series. Learn MVC in 16 hours:- https://www.youtube.com/watch?v=Lp7nSImO5vk Learn AngularJS Step by Step:- https://www.youtube.com/watch?v=0kmdjqgO9IY Learn Design Pattern in 8 hours:- https://www.youtube.com/watch?v=YDobmucohqk Learn C# and .NET in 60 days:- https://www.youtube.com/watch?v=yh2SrzCkNQA Learn MSBI in 32 hours:- https://www.youtube.com/watch?v=mGPJx3ocFgg Learn SharePoint Step by Step in 8 hours:- https://youtu.be/C2fW76SwJNU
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