Visual C#

Quite often when dealing with an API or some other external service, you will find that you get Unix timestamps returned to you or alternatively have to provide a timestamp in Unix form when sending a request back. Since you are going to be running your .NET code on a windows machine, you don’t have a built in way to get the time in Unix format. It is pretty simple to obtain a Unix timestamp though. Here is what you need to do to convert C# DateTime object to a Unix timestamp.

The following helper method can be used to convert a standard datetime object into a Unix timestamp value. The value is quite large and will get bigger as time goes on, so make sure to use an appropriate variable type. Long will work fine for this scenario.

It’s a pretty simple method with little to explain. Its worth noting that you need to keep this as a long. Int is not going to be big enough to hold the time value.

If you want to do things in reverse. I.e. Convert a Unix timestamp back to a C# DateTime object, you can use the following helper method.

 

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You are looking to create some sort of HTML element on your site that when clicked will trigger a file download. Seems like a pretty simple request, but there is a little more to it then first appears. By default web browsers will have a set way to handle certain file formats. For example, if you wanted a user to be able to download an image file, simply putting the path of the image in the href, would just open the image in a new tab/window rather than actually download the file. Here is what you need to download a file using ASP MVC.

In order to do this you will need to setup an “ActionResult” on one of your controllers. This means you will be setting the href or source of the link to the URL of the controller. For this example i created a controller called “Services” a method in the controller called “DownloadFile” and this method accepted a value that represented the file. For this you could use some kind of ID that lets you know where to find the file or simple URL encode the file path. This method is probably the easiest, but is not secure. If you are using a public site, you are going to have to setup a DB table to manage the files so that each row has a unique ID that you can use to identify the file. This is what i have done for this example.

I have created a custom document object that works with the DB table. Passing the ID of the row in the constructor (i know its bad practice..but its much quicker). This will pull all of the file information from the database including the path of the file on the disk.

The file path returns a value like “C:/myfiles/somefile.pdf”.

In order to gain access to this file using a download link you will setup a link like the following.

And there you have it, this will trigger the file download in your browser. This can be used to download any file from a windows machine. So long as your server has access to the drive, the file can be downloaded. This means you can download files that are outside of the root of your web servers home directory.

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File downloads can be a bit of a nuance sometimes as web browsers often support a lot of document types. Simply adding the file path to the href of a html element, wont be enough for you to be able to download the file. There are dozens of work arounds to make this work, but using an ASP.NET ashx handler is definitely one of the cleanest methods to do it using code.

I will paste the contents of the entire ashx file below as the script is very simple. This solution will only work if you are using the non razor MVC models that are part of the ASP.NET framework. First you will need to create a new “Generic Handler” this will create a file with a .ashx extension. Once this is done you can point all of your links to this page when you want to download a file. There are many ways you can direct the downloads to this page. To keep things very simple, I have setup the script to accept the file path in the URL of the request.

In order to make the request work you will need to urlencode the value that is being passed into the url. The following code will be all you need to setup the url.

You could alternatively use javascript or pretty much anything that is capable of generating a request to your download script. This method has massive security risks, so please take this into consideration. This code will be enough to get a working prototype for you to built upon. This should never be used in any public facing code without some security measures being implemented to stop people tampering with the URL.

 

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This can be done in the RouteConfig.cs. You can set the default route that will be used to display the home page. You can find this file in Project->App_Start->RouteConfig.cs. The config inside this file will let you set default home page for ASP.NET razor MVC websites. The contents of the default file should look something like this.

The line that you need in particular to change the default homepage of an ASP MVC site is the defaults section. Change the name of the controller to whatever you want. The action for this will be the name of the method that you want to call within that controller. Once you have added this information your server should now be displaying this page as the default home page for your site.

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When you want to access a session from an ashx file you will find that using context.Session[“value”] , will not allow you to access the session variables from the previous file where the session was available from. This is expected behavior and based on some guides Ihave seen, is often over complicated. Rather than building a work around that will pass the values through the URL or some other method, it is actually quite easy to just gain access to this session value again from the ashx file by implementing a single class.

To implement another class in your current class you need to alter the class declaration. By altering the class declaration and implementing the IRequiresSessionState class, you will be able to access a session information from an ashx file, without needing to built a messy work around that requires data to be sent through a different, less convenient medium. The class you need to implement is “System.Web.SessionState.IRequiresSessionState”. The class declaration should look something like this.

This is all you need to access a session from an ashx file. You dont need to be writing anything to a particular session file or creating any fancy methods. Using this method is all you need. This will save you the trouble of building a messy work around.