1. Vba Upload File To Web Server Software

(Visual Basic 6.0) Upload Files to a Web Server - Simplest Example. This is the simplest example for uploading some files to a web server. The BlockingUpload call is synchronous and returns when the upload is finished (or failed). A server-side C# example showing how to receive an upload is located at C# ASP.NET Code to Receive Upload.

• Writing the code to upload images to a server from scratch seems like a very daunting task. I'm going to make a very simple upload form to demonstrate how file data works and can be transferred. In this tutorial, we're going to build an upload form with HTML, send the files with JavaScript, and process and upload them with PHP.
• This step-by-step article describes how to upload a file to a Web server by using Visual C#.NET. In this article, you create a Microsoft ASP.NET file (WebForm1.aspx) and its related code-behind file (WebForm1.aspx.cs) to upload files to a directory that is named Data.

By Steve Smith

ASP.NET MVC actions support uploading of one or more files using simple model binding for smaller files or streaming for larger files.

Uploading small files with model binding

To upload small files, you can use a multi-part HTML form or construct a POST request using JavaScript. An example form using Razor, which supports multiple uploaded files, is shown below:

Vba Upload File To Web Server Software

In order to support file uploads, HTML forms must specify an enctype of multipart/form-data. The files input element shown above supports uploading multiple files. Omit the multiple attribute on this input element to allow just a single file to be uploaded. The above markup renders in a browser as:

The individual files uploaded to the server can be accessed through Model Binding using the IFormFile interface. IFormFile has the following structure:

Warning

Don't rely on or trust the FileName property without validation. The FileName property should only be used for display purposes.

When uploading files using model binding and the IFormFile interface, the action method can accept either a single IFormFile or an IEnumerable<IFormFile> (or List<IFormFile>) representing several files. The following example loops through one or more uploaded files, saves them to the local file system, and returns the total number and size of files uploaded.

Warning: The following code uses GetTempFileName, which throws an IOException if more than 65535 files are created without deleting previous temporary files. A real app should either delete temporary files or use GetTempPath and GetRandomFileName to create temporary file names. The 65535 files limit is per server, so another app on the server can use up all 65535 files.

Files uploaded using the IFormFile technique are buffered in memory or on disk on the web server before being processed. Inside the action method, the IFormFile contents are accessible as a stream. In addition to the local file system, files can be streamed to Azure Blob storage or Entity Framework.

To store binary file data in a database using Entity Framework, define a property of type byte[] on the entity:

Specify a viewmodel property of type IFormFile:

Note

IFormFile can be used directly as an action method parameter or as a viewmodel property, as shown above.

Copy the IFormFile to a stream and save it to the byte array:

Note

Use caution when storing binary data in relational databases, as it can adversely impact performance.

Uploading large files with streaming

If the size or frequency of file uploads is causing resource problems for the app, consider streaming the file upload rather than buffering it in its entirety, as the model binding approach shown above does. While using IFormFile and model binding is a much simpler solution, streaming requires a number of steps to implement properly.

Note

Any single buffered file exceeding 64KB will be moved from RAM to a temp file on disk on the server. The resources (disk, RAM) used by file uploads depend on the number and size of concurrent file uploads. Streaming isn't so much about perf, it's about scale. If you try to buffer too many uploads, your site will crash when it runs out of memory or disk space.

The following example demonstrates using JavaScript/Angular to stream to a controller action. The file's antiforgery token is generated using a custom filter attribute and passed in HTTP headers instead of in the request body. Because the action method processes the uploaded data directly, model binding is disabled by another 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. Once all sections have been read, the action performs its own model binding.

The initial action loads the form and saves an antiforgery token in a cookie (via the GenerateAntiforgeryTokenCookieForAjax attribute):

The attribute uses ASP.NET Core's built-in Antiforgery support to set a cookie with a request token:

Angular automatically passes an antiforgery token in a request header named X-XSRF-TOKEN. The ASP.NET Core MVC app is configured to refer to this header in its configuration in Startup.cs:

The DisableFormValueModelBinding attribute, shown below, is used to disable model binding for the Upload action method.

Since model binding is disabled, the Upload action method doesn't accept parameters. It works directly with the Request property of ControllerBase. A MultipartReader is used to read each section. The file is saved with a GUID filename and the key/value data is stored in a KeyValueAccumulator. Once all sections have been read, the contents of the KeyValueAccumulator are used to bind the form data to a model type.

The complete Upload method is shown below:

Warning: The following code uses GetTempFileName, which throws an IOException if more than 65535 files are created without deleting previous temporary files. A real app should either delete temporary files or use GetTempPath and GetRandomFileName to create temporary file names. The 65535 files limit is per server, so another app on the server can use up all 65535 files. Rh factor hard groove rarest.

Troubleshooting

Below are some common problems encountered when working with uploading files and their possible solutions.

Unexpected Not Found error with IIS

The following error indicates your file upload exceeds the server's configured maxAllowedContentLength:

The default setting is 30000000, which is approximately 28.6MB. The value can be customized by editing web.config:

This setting only applies to IIS. The behavior doesn't occur by default when hosting on Kestrel. For more information, see Request Limits <requestLimits>.

Null Reference Exception with IFormFile

If your controller is accepting uploaded files using IFormFile but you find that the value is always null, confirm that your HTML form is specifying an enctype value of multipart/form-data. If this attribute isn't set on the <form> element, the file upload won't occur and any bound IFormFile arguments will be null.

Let’s start this the manual way to get a feel for how this part works. Open up your Command Prompt in Windows, command prompt works in a similar way to the Interpreter, so it helps to know what’s going on to hep understand the VB code later.

On the first line in Command Prompt type in the following line, replacing myserver.com with your ftp server.

The two parts to this line are ‘ftp’, which tells the command you are connecting via ftp protocol, and the second part ‘ftp.myserver.com’ which you will put in the address of your file server.

You will then be prompted for your user name and password on separate lines. Type these in and press enter to see the following on a separate line

This means we are connected and ready to upload or download.

To change the local directory type in the following line.

This will set the location where the files we wish to upload or download are stored on our computer. Also note, the quotes are only needed where this is a space in the directory name. You will receive a message line starting with OK, if the directory change was successful.

To change the remote directory type in the following line.

Again, you will receive a message line starting with OK if the remote folder change was successful.

Now to send a file. Type to following line into command prompt and press enter, replacing myfile.png with your desired file.

This line is telling the command prompt to send file the C:/Users/Me/My Documents/myfile.png to the your/remote/destination/ folder on the server, of course your details will be in there. You will then see a line stating the following

What does ‘put’ mean? It simply means put this file there. What if I want to send all the files in the folder? Then we use ‘mput’ with a wildcard as below…

Will send all .png files in the folder

Will send all files in the folder

Will send all files starting with an ‘a’ in the folder

Once we have finished our uploads, we can type in ‘bye’ on a new line to close the connection, then 'exit' to close the command prompt.

Now we’ve covered those basics we can get stuck into the Visual Basic aspect in the next step.