This version of the Save method is discussed next. The Save method contains a lot of code, but most of it is pretty standard ADO. NET code:. This code creates a SqlConnection and a SqlCommand object and then creates a number of parameters. Most of them are pretty straight forward, but the fileUrl and fileData parameters need a bit more explanation highlighted in the code above.
When the DataStoreType passed in equals Database , it means the actual file is stored in the database. In that case, the fileData property is assigned to the value of the prmFileData parameter. The type of that parameter is SqlDbType. VarBinary , which corresponds to the data type of the column in the database. Image instead. Since the file has already been converted to a byte array in the calling code, all you need to do here is assign the fileData variable to the parameter's Value property.
Value is passed instead, so null is stored in the database. Finally, the Command object is executed against an open database connection and the result of the ExecuteNonQuery call is stored in a temporary variable.
Notice that when the FileSystem is used, the Save method also saves the file to disk:. To save the file, the byte array is converted back to a Stream again, which is then written to disk using another Stream object. For the file name, this code uses the filePath parameter passed to the Save method. As an alternative to this solution, you can decide to call the SaveAs method on the FileUpload control in the code behind of UploadFile. This is easier, as the SaveAs method takes care of it all; all you need to do is pass a file name.
However, it also means you're spreading logic across your application. By encapsulating all the code into a single File class, your application becomes easier to maintain and extend. As another alternative, you could pass the entire FileUpload control to the Save method, and have that method call its SaveAs method. Personally, I don't like that solution too much, as it ties the File class to a WebControl , which makes it harder to reuse it in other type of applications.
Again, the varbinary max data type is used for the fileData parameter, to line up with the SqlParameter and the column for the file in the database as you saw earlier. With the Save operation done, the next thing to look at is displaying files. To display files in a web browser, there are two scenario's to consider: displaying lists of files, and displaying or downloading a single file. I'll look at the list first, followed by the single file. The page Default.
It also contains two columns that allow you to download a file and - in certain circumstances - view the file in-line in the browser. In Figure 2 you can see that only some files have the View link enabled. Some code in the code behind looks at the content type of the file in each row, and enables the View link when the file can be viewed in-line in the browser. That's the case for images jpg, gif for example and other files that the browser can usually handle Word files, Excel spreadsheets.
Other files that can't be viewed directly, but need a separate application Zip and Rar files for example can only be downloaded. You'll see the code for this a little later. You could opt to implement the GetList method in the File class and remove the entire FileInfo class.
However, I have chosen to implement it like this for performance reasons. In most scenarios, when you display a list of files, you don't need the actual files; all you need is some meta data like the name and unique ID. By implementing a simple, and read-only class FileInfo , you get all the data you need without the overhead of retrieving all the files from the database.
When this control gets its data, it calls the static GetList method that returns a generics List of FileInfo objects:. Again, most of this code is pretty straight forward.
To make the code a bit more readable, the FileInfo class has a constructor that accepts a SqlDataReader. This way, you only need a single line of code in the while loop to create a FileInfo instance and add it to the list. The constructor that accepts the SqlDataReader looks like this:.
Since all fields are required in the database, there's no need to check for null values. At the end of the GetList method, the list with FileInfo objects is returned to the calling code where it's bound to the GridView.
For each FileInfo object that is added to the GridView , it fires its RowDataBound event that is used to determine whether the View link should be enabled or not:.
The FileInfo 's ContentType is then used to determine whether the file is viewable in the browser or not. In the example above, this is only done for. For all other files, the link is retrieved with the FindControl method of the row and then its Enabled property is set to false. When you click the Download or View link, you're take to DownloadFile. The code behind of these files are pretty similar, but there are a few interesting differences worth looking at. Both pages start by getting a File object from the database by calling File.
This method is pretty straight forward, and uses the same principle as the FileInfo class by implementing a constructor that accepts a SqlDataReader object to fill the private fields:.
The first four fields are retrieved directly from the reader. The code then checks if the column FileData has a value that isn't null. If that's the case, the value is casted to a byte array and assigned to the fileData field.
Notice that containsFile is also set to true to indicate that the File instance contains the actual file bytes. The public ContainsFile property is used in the download and view pages to determine whether the File instance contains the actual file bytes, or that they should search for the files on the server's hard drive.
In the else clause, the fileUrl with the virtual path to the file on disk, starting from the virtual Uploads folder is set, and containsFile gets a value of false.
Once the File object is returned, DownloadFile. Then it uses either the BinaryWrite or the WriteFile method of the Response object, based on the fact whether the File object contains the actual file data:. In both cases, this forces the browser to display a File Download dialog that allows the user to save the file to disk :. Figure 4 - The File Download Dialog.
The ViewFile. It then switches between BinaryWrite and Redirect to send the file to the browser where it's displayed in line:. With the code to download or view an uploaded file, we've come full circle. You can now upload files to the server and store them on disk or in a database depending on your own preferences or requirements. You can list the files in a GridView and offer your users a way to download or display them.
Storing your uploaded files in a SQL Server database can be very convenient. It allows you to easily relate the uploaded files to other records in the database. However, there are also some disadvantages that you need to be aware of. One is performance, while another is increased backup-time. Whether you should save your files on disk or in a database depends on your own preferences and requirements. This article showed you how to upload your files and store them in a database or on disk depending on a simple configuration switch.
When you store them in a database, you can use the Image or the varbinary max data type. When you store them on disk, you need to ensure that the account used by the web server has sufficient permissions to write to the Uploads folder. Now we can use DatabaseContext class as service for dependency injection in the entire application.
The next step we are going to add a controller. We are going to add a controller with Name Demo Controller after adding controller we have default Index action method in it.
And also, for accessing DatabaseContext in DemoController, we are going to use Constructor injection. Next step we are going to valid Length of the posted file if it is greater then zero then we are going generate new file name, and then next we are going to create object of Files class and assign IformFile values to files object which we have created and then we are going to pass Files Model to Add method of DbContext which set entity set to Added When we call context.
SaveChanges then an Insert statement is generated and executed by the database. After completed with adding Index Action Method along with constructor injection for injecting DatabaseContext dependency which uses for inserting uploaded file to the database. Next, we are going to Run Application and Test it by uploading an image.
Debug View While Uploading file. NET Developer and working on. Net Web Technology Asp. Because the action method processes the uploaded data directly, form model binding is disabled by another custom filter.
Within the action, the form's contents are read using a MultipartReader , which reads each individual MultipartSection , processing the file or storing the contents as appropriate. After the multipart sections are read, the action performs its own model binding. The initial page response loads the form and saves an antiforgery token in a cookie via the GenerateAntiforgeryTokenCookieAttribute attribute.
The attribute uses ASP. NET Core's built-in antiforgery support to set a cookie with a request token:. ConfigureServices using Razor Pages conventions :. Since model binding doesn't read the form, parameters that are bound from the form don't bind query, route, and header continue to work.
The action method works directly with the Request property. A MultipartReader is used to read each section. After the multipart sections are read, the contents of the KeyValueAccumulator are used to bind the form data to a model type. The complete StreamingController. UploadDatabase method for streaming to a database with EF Core:. UploadPhysical method for streaming to a physical location:. In the sample app, validation checks are handled by FileHelpers. The sample app's FileHelpers class demonstrates a several checks for buffered IFormFile and streamed file uploads.
For processing streamed files, see the ProcessStreamedFile method in the same file. The validation processing methods demonstrated in the sample app don't scan the content of uploaded files. Although the topic sample provides a working example of validation techniques, don't implement the FileHelpers class in a production app unless you:. Never indiscriminately implement security code in an app without addressing these requirements.
Scanning files is demanding on server resources in high volume scenarios. If request processing performance is diminished due to file scanning, consider offloading the scanning work to a background service , possibly a service running on a server different from the app's server. Typically, uploaded files are held in a quarantined area until the background virus scanner checks them.
When a file passes, the file is moved to the normal file storage location. These steps are usually performed in conjunction with a database record that indicates the scanning status of a file.
By using such an approach, the app and app server remain focused on responding to requests. The uploaded file's extension should be checked against a list of permitted extensions. For example:. A file's signature is determined by the first few bytes at the start of a file. These bytes can be used to indicate if the extension matches the content of the file. The sample app checks file signatures for a few common file types. In the following example, the file signature for a JPEG image is checked against the file:.
To obtain additional file signatures, see the File Signatures Database and official file specifications. Never use a client-supplied file name for saving a file to physical storage. Create a safe file name for the file using Path. GetRandomFileName or Path. GetTempFileName to create a full path including the file name for temporary storage. Outside of Razor, always HtmlEncode file name content from a user's request. For more information, see Upload files in ASP. NET Core. Use the InputFile component to read browser file data into.
NET code. By default, the user selects single files. Add the multiple attribute to permit the user to upload multiple files at once. To read data from a user-selected file, call IBrowserFile. OpenReadStream on the file and read from the returned stream.
For more information, see the File streams section. OpenReadStream enforces a maximum size in bytes of its Stream. Reading one file or multiple files larger than , bytes KB results in an exception. This limit prevents developers from accidentally reading large files in to memory. Avoid reading the incoming file stream directly into memory. For example, don't copy file bytes into a MemoryStream or read as a byte array.
These approaches can result in performance and security problems, especially in Blazor Server. Instead, consider copying file bytes to an external store, such as a blob or a file on disk. If you need access to a Stream that represents the file's bytes, use IBrowserFile. In the following examples, browserFile represents the uploaded file and implements IBrowserFile :. A component that receives an image file can call the BrowserFileExtensions.
RequestImageFileAsync convenience method on the file to resize the image data within the browser's JavaScript runtime before the image is streamed into the app. The following example demonstrates multiple file upload in a component. GetMultipleFiles allows reading multiple files. Specify the maximum number of files to prevent a malicious user from uploading a larger number of files than the app expects.
File allows reading the first and only file if the file upload doesn't support multiple files. C files require an explicit using directive.
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