Uploading and returning files in ASP. NET MVCIndex. 1. Brief. Uploading and returning files in an ASP. NET MVC application is very simple. The POSTed files are available as parameters directly in actions through model binding. Wcf Rest Receive File Large Chunks Of Turquoise1. Brief. Uploading and returning files in an ASP. NET MVC application is very simple. The POSTed files are available as parameters directly in actions through model. The files in the server can be easily sent as response to the clients through its rich support of action results. There are already plenty of articles written on this subject. So why another article Well, in this article I gathered the important concepts that are scattered. Im sure this article will help the MVC programmers to increase their grip on the framework. Thanks for all the readers who pointed out the errors and typos in the article. I really appreciate them. How to upload a file Basics. POSTing a file to the server is quite simple. All we need is a html form having encoding type set to multipartform data and a file input control. Photo lt label. Many popular web frameworks such as Django, Microsoft ASP. NET, Microsoft WCF, and those built on PHP do not have mechanisms to handle serialization based on Content. Upload. Listing 1. Simple file upload html form. An important thing developers forget sometimes is setting the encoding typeenctype to multipartform data. As default the encoding type is. ASCII data. and binary data. When you post the form the Content Type header is set to multipartform data. Calendario Pirelli 2010. If you forget setting the proper encoding type then only the. Reading files from request. The POSTed files are available in Http. File. Collection. Base of Request. Files. In the below listing we can see how to read the POSTed file from the request and save to the server. Action. Result Upload. D Temp. Http. Posted. File. Base photo Request. Filesphoto. ifphoto null photo. Content. Length 0. Name Path. Get. File. Namephoto. File. Name. Save. AsPath. Combinedirectory, file. Name. return Redirect. To. ActionIndex. Listing 2. Upload action. Instead of manually reading the file from the Request, by taking the advantage of model binding the file can be made directly available as a parameter in the action as shown in the below listing. Action. Result UploadHttp. Posted. File. Base photo. D Temp. ifphoto null photo. Content. Length 0. Name Path. Get. File. Namephoto. File. Name. Save. AsPath. Combinedirectory, file. Name. return Redirect. To. ActionIndex. Listing 3. Using Http. Posted. File. Base as action parameter. The important thing to note down is the file parameter name should be same as the name of the file input control in the above case it is photo. Http. Posted. File. Base. Http. Posted. File. Base is an abstract class that contains the same members as in Http. Posted. File. Prior to the. NET framework 3. 5 version. Http. Posted. File which is concrete and sealed making the code hard to unit test. The Http. Posted. File. Base is created to substitute Http. Posted. File in MVC applications for better unit testing. So wherever you need to read files, I advise you to use Http. Posted. File. Base instead of Http. Posted. File. An important thing to note down is we cant directly substitute Http. Posted. File with Http. Posted. File. Base because Http. Posted. File is still the same, not derives from any type. In some cases we need to convert Http. Posted. File. Base to Http. Posted. File and we can achieve that using the Http. Posted. File. Wrapper. Behind the scenes. As many of us already aware, its the model binding feature that maps the POSTed file to Http. Posted. File. Base in the action parameter. But what we are interested here is to know the supporting classes. The model binding feature relies on two types of components binders and value providers. The value providers are the components that gets the value needed from the particular source query strings, form etc. The binders are the components that really fills the properties of a model or the parameters in the action with those values. The MVC framework is designed in such a way that these two components are loosely coupled and hence a binder dont need to worry about which value provider. Http. Posted. File. Base. Model. Binder. When you have a single instance of Http. Posted. File. Base as an action parameter or a property in model then mapping the file is completely done by the Http. Posted. File. Base. Model. Binder and no value providers are used in this case. You may think why no value providers are used in this case. Request. Files collection. Http. File. Collection. Value. Provider. When model binding collection of POSTed files, the Http. File. Collection. Value. Provider comes into play along with the Default. Model. Binder. The Http. File. Collection. Value. Provider which derives from the Dictionary. Value. Provider stores all the POSTed files as a dictionary and feeds the Default. Model. Binder. with files whenever it needs to map a parameter or property of type Http. Posted. File. Base. Uploading multiple files. So uploading a single file and reading it from the server is quite easy, all we need is to set the Http. Posted. File. Base type as a parameter in the corresponding action method. How about reading multiple files POSTed to the server We can easily achieve this by setting an IEnumerablelt Http. Posted. File. Base as action parameter. Here is a sample html form to upload multiple files. Photo lt label. Upload. Listing 4. Form to upload multiple files. Below is the action that handles the POST request of the form. Action. Result UploadIEnumerablelt Http. Posted. File. Base files. Save. As. return Redirect. To. ActionIndex. Listing 5. Using IEnumerablelt Http. Posted. File. Base as action parameter to receive multiple POSTed files. The important thing is the name of the file input controls should match the rules of model binding. Using view models to validate POSTed files. Like any other input data the POSTed files to the server also needs validation. For example, in the case of image we need the file should be one of the supported image. When we use the Http. Posted. File. Base directly as action parameter then we have to validate the file manually as shown in the below listing. Action. Result UploadHttp. Posted. File. Base photo. Content. Length 0. D Temp. if photo. Content. Length 1. Model. State. Add. Model. Errorphoto, The size of the file should not exceed 1. KB. return View. Types new jpg, jpeg, png. Ext System. IO. Path. Get. Extensionphoto. File. Name. Substring1. Types. Containsfile. Ext. Model. State. Add. Model. Errorphoto, Invalid type. Only the following types jpg, jpeg, png are supported. View. var file. Name Path. Get. File. Namephoto. File. Name. photo. Save. AsPath. Combinedirectory, file. Name. return Redirect. To. ActionIndex. Listing 6. Uploading file with validations. In the above action we have done couple of validations against the uploaded file. Instead of doing it manually it would be great. Lets create a view model that wraps Http. Posted. File. Base as a property which is decorated with data annotation attributes. Upload. File. Model. File. Size1. 02. File. Typesjpg,jpeg,png. Http. Posted. File. Base File get set. Listing 7. View model. Note that the validation attributes applied over the File property are custom ones and not exists in the data annotations assembly. Creating custom validation attribute is not a difficult job All we have to do is derive a class from Validation. Attribute and override the Is. Valid and Format. Error. Message methods. Here are our implementations for File. Size. Attribute and File. Types. Attribute. File. Size. Attribute. File. Size. Attribute Validation.