Asp file upload control

If it returns false , display a message to the user indicating that the control does not contain a file. Do not check the PostedFile property to determine whether a file to upload exists because, by default, this property contains 0 bytes. As a result, even when the FileUpload control is blank, the PostedFile property returns a non-null value. When you call the SaveAs method, you must specify the full path of the directory in which to save the uploaded file.

If you do not explicitly specify a path in your application code, an exception is thrown when a user attempts to upload a file. This behavior helps keep the files on the server secure by preventing users from being able to write to arbitrary locations in your application's directory structure, as well as preventing access to sensitive root directories.

The SaveAs method writes the uploaded file to the specified directory. Therefore, the ASP. NET application must have write access to the directory on the server. There are two ways that the application can get write access. You can explicitly grant write access to the account under which the application is running, in the directory in which the uploaded files will be saved.

Alternatively, you can increase the level of trust that is granted to the ASP. NET application. To get write access to the executing directory for the application, the application must be granted the AspNetHostingPermission object with the trust level set to the AspNetHostingPermissionLevel. Medium value. Increasing the level of trust increases the application's access to resources on the server. Note that this is not a secure approach, because a malicious user who gains control of your application will also be able to run under this higher level of trust.

It is a best practice to run an ASP. NET application in the context of a user with the minimum privileges that are required for the application to run. For more information about security in ASP. One way to guard against denial of service attacks is to limit the size of the files that can be uploaded by using the FileUpload control.

You should set a size limit that is appropriate for the types of files that you expect to be uploaded. The default size limit is kilobytes KB , or 4 megabytes MB. You can allow larger files to be uploaded by setting the maxRequestLength attribute of the httpRuntime element. To increase the maximum allowable file size for the entire application, set the maxRequestLength attribute in the Web. To increase the maximum allowable file size for a specified page, set the maxRequestLength attribute inside the location element in Web.

For an example, see location Element ASP. NET Settings Schema. If your users encounter this error message, increase the value of the memoryLimit attribute in the processModel of element the Web.

The memoryLimit attribute specifies the maximum amount of memory that a worker process can use. If the worker process exceeds the memoryLimit amount, a new process is created to replace it, and all current requests are reassigned to the new process. To control whether the file to upload is temporarily stored in memory or on the server while the request is being processed, set the requestLengthDiskThreshold attribute of the httpRuntime element.

This attribute enables you to manage the size of the input stream buffer. The default is bytes. The value that you specify should not exceed the value that you specify for the maxRequestLength attribute. The FileUpload control is designed to be used only in postback scenarios and not in asynchronous postback scenarios during partial-page rendering. When you use a FileUpload control inside an UpdatePanel control, the file must be uploaded by using a control that is a PostBackTrigger object for the panel.

UpdatePanel controls are used to update selected regions of a page instead of updating the whole page with a postback. Initializes a new instance of the FileUpload class. Gets or sets the application-relative virtual directory of the Page or UserControl object that contains this control. Gets the collection of arbitrary attributes for rendering only that do not correspond to properties on the control.

Gets or sets the algorithm that is used to generate the value of the ClientID property. Gets a character value representing the separator character used in the ClientID property. Gets the HttpContext object associated with the server control for the current Web request.

Gets a ControlCollection object that represents the child controls for a specified server control in the UI hierarchy. Gets a value indicating whether a Style object has been created for the ControlStyle property. This property is primarily used by control developers. Gets a reference to the naming container if the naming container implements IDataItemContainer. Gets a reference to the naming container if the naming container implements IDataKeysControl. Gets or sets a value indicating whether the server control persists its view state, and the view state of any child controls it contains, to the requesting client.

Gets an array of the bytes in a file that is specified by using a FileUpload control. Gets a Stream object that points to a file to upload using the FileUpload control. Gets the name of a file on a client to upload using the FileUpload control. Gets a value indicating whether the current server control's child controls have any saved view-state settings.

Gets a value indicating whether the FileUpload control contains a file. Gets a value indicating whether the control participates in loading its view state by ID instead of index. Gets a reference to the server control's naming container, which creates a unique namespace for differentiating between server controls with the same ID property value.

Gets a reference to the Page instance that contains the server control. Gets the underlying HttpPostedFile object for a file that is uploaded by using the FileUpload control. Gets information about the container that hosts the current control when rendered on a design surface. Gets a collection of text attributes that will be rendered as a style attribute on the outer tag of the Web server control. Gets a value that indicates whether the control should set the disabled attribute of the rendered HTML element to "disabled" when the control's IsEnabled property is false.

This property is used primarily by control developers. Gets the virtual directory of the Page or UserControl that contains the current server control. Gets or sets a value that indicates whether the control checks client input from the browser for potentially dangerous values.

Gets a dictionary of state information that allows you to save and restore the view state of a server control across multiple requests for the same page. Gets a value that indicates whether the StateBag object is case-insensitive. Called after a child control is added to the Controls collection of the Control object. Copies any nonblank elements of the specified style to the Web control, overwriting any existing style elements of the control.

This method is primarily used by control developers. Gathers information about the server control and delivers it to the Trace property to be displayed when tracing is enabled for the page. Sets the cached ClientID value to null.

Deletes the view-state and control-state information for all the server control's child controls. Copies the properties not encapsulated by the Style object from the specified Web server control to the Web server control that this method is called from.

This method is used primarily by control developers. Called by the ASP. NET page framework to notify server controls that use composition-based implementation to create any child controls they contain in preparation for posting back or rendering. Creates a new ControlCollection object to hold the child controls both literal and server of the server control.

Creates the style object that is used internally by the WebControl class to implement all style related properties. Binds a data source to the invoked server control and all its child controls with an option to raise the DataBinding event. Determines whether the server control contains child controls. If it does not, it creates child controls. Searches the current naming container for a server control with the specified id parameter.

Searches the current naming container for a server control with the specified id and an integer, specified in the pathOffset parameter, which aids in the search. You should not override this version of the FindControl method. Gets the Type of the current instance. Returns the prefixed portion of the UniqueID property of the specified control. Restores control-state information from a previous page request that was saved by the SaveControlState method.

Restores view-state information from a previous request that was saved with the SaveViewState method. Creates a shallow copy of the current Object. Copies any nonblank elements of the specified style to the Web control, but will not overwrite any existing style elements of the control. Determines whether the event for the server control is passed up the page's UI server control hierarchy. Raises the DataBinding event. Raises the Init event. Raises the Load event.

Raises the PreRender event for the FileUpload control. A FileUpload server control is a control that displays a box and a browse button on the web page. It allows the user to select a file from the local storage and upload it to the server. Why did I use the term server control? Well, because like all other server controls, ASP.

It lets the users select a file and upload it to the server. The drag and drop feature ultimately generates the same code. So, how does the FileUpload mechanism work? When the user selects a file from his local storage, the FileUpload control initiates an object which stores the basic information about the file.

This information contains the file name, extension, directory path, file size, etc. The object has a property HasFile which is then set to true. This property determines whether the user has selected any file or not. It has only been selected by the user. The browse button generated by the FileUpload control does not actually upload the file. This has to be done by writing a piece of code that instructs the FileUpload control to save a copy of the file in a path on the server.

When this piece of code is triggered, the FileUpload control simply sends the file over HTTP S protocol to the server and stores it at the specified path. The ASP. Net FileUpload control comes with certain pre-defined properties.

These properties are converted to attributes in the native HTML code. They help define additional behavior for the FileUpload control. AllowMultiple: This property gets or sets a value that permits or restricts the user to select multiple files simultaneously. The default value is false, which means the user is not allowed to select multiple files by default. BackColor, ForeColor: This property gets or sets the background and the foreground color of the control.

Enabled: This property gets or sets the value indicating whether the control is enabled or disabled. And here is the CodeBehind code required to handle the upload:. As you can see, it's all relatively simple. Once the UploadButton is clicked, we check to see if a file has been specified in the upload control. If it has, we use the FileUpload controls SaveAs method to save the file.

We use the root of our project we use the MapPath method to get this as well as the name part of the path which the user specified.