However, in our web page, there more than files in the website. It would take a long time to copy and paste the names using the item enumerator. The new example will show how to create an array with the list of files. We will first go to www. We will pivot the table to create a list of files in the format requested by C. To do this we are going to replace ; with ". When you execute the code, you will be able to see all the files downloaded in the local folder.
If you do not want to work with arrays in C like we did in the example 3, there is another option. This example will import the list of files to SQL Server and then download the files using the list. We will create a table in that database. In the Name of the table or view, press the New Button:. In SQLStatements do a select filename from listoffiles:.
In Result Set, specify 0 as the Result Name. In Variable Name, add the variable named filename created in the example This enumerator will get the information from the SQL table created.
In ADO object source variable, select the filename variable and in Enumeration mode select Rows in the first table:. In variable Mapping, select the User:filename variable and in Index put 0. A typical error is that the value DBNull is assigned to variable. In the progress page, you can see the error message:. Error: The type of the value DBNull being assigned to variable "User::filename" differs from the current variable type String. Variables may not change type during execution.
Variable types are strict, except for variables of type Object. This error occurs because the parameter is a string and it is compared with a database object. To fix this problem change the filename variable data type to object:. In this article, we show how to download a single file and 3 ways to download multiple files.
The item iterator is the best option if there are few files. The second option C array is good if it is easy to convert the list of files to an array. In this case, the reference is to Newtonsoft. Note, however, this is a directive designed for referencing files in the file system.
Using declarations are another C language feature allowed in C scripting, one that Figure 2 leverages several times. Note that just as in C , a using declaration is scoped to the file. Therefore, if you called load Spell. Json declarative outside the Spell. In other words, using Newtonsoft. Json from within Spell. Note that the C 6. My name is Inigo Montoya".
As noted, csi. Like the csi. First, it includes syntax color coding and IntelliSense. Similarly, compilation occurs in real time, as you edit, so syntax errors and the like will automatically be red-squiggle-underlined.
NET statements—they have significantly different purposes. The C Immediate Window is bound directly to the debug context of your application, thus allowing you to inject additional statements into the context, examine data within the debug session, and even manipulate and update the data and debug context. Similarly, the Command Window provides a CLI for manipulating Visual Studio, including executing the various menus, but from the Command Window rather than from the menus themselves.
Executing the command View. C Interactive, for example, opens the C Interactive Window. Like csi. NET snippets to verify your understanding without having to start yet another Visual Studio console or unit testing project. Instead of having to launch a separate program, however, the C Interactive Window is hosted within Visual Studio, where the developer is presumably already residing.
At the end of the current submission, replace the current submission with a subsequent submission after having previously navigated backward.
Furthermore, the CSharpInteractive. The combination of these two files is why you can use Console. WriteLine and Environment. CurrentDirectory rather than the fully qualified System. WriteLine and System. In addition, referencing assemblies such as Microsoft. CSharp enables the use of language features like dynamic without anything further.
One thing to keep in mind about the C script syntax is that much of the ceremony important to a standard C becomes appropriately optional in a C script. The last declaration shadows any earlier declaration. Another important item to be conscious of is the behavior of the command-ending semicolon.
Statements variable assignments, for example require a semicolon. When the DownloadFileCompleted event is fired, the Set method on the AutoResetEvent sends a signal that allows the code to proceed to the next statement. Note that the use of AutoResetEvent as shown above, is a neat little trick that can be applied to any other asynchronous methods you want to call and subsequently wait for completion.
Although the above example works, there is a cleaner way to achieve the same result, providing you are targeting. NET Framework 4. NET Core 2. NET Standard 2. By using the await keyword when calling the DownloadFileTaskAsync method, the code will wait until the file download has completed, while at the same time carrying out the download asynchronously and firing the progress events.
Note that whatever method you use the above code within needs to be marked with the async keyword. Before attempting to use the HttpClient class, make sure you have the appropriate using statement in place, as follows.
Note that even though HttpClient implements IDisposable it is recommended that you create one instance of HttpClient and reuse this throughout your program to avoid problems such as socket exhaustion.
As you can see from the above example, the code required to download a file using HttpClient is a little lower level compared to using WebClient , since we need to work with streams directly. Nonetheless, the code is still straightforward to follow along with.
Note that as per the previous example, whatever method you use the above code within needs to be marked with the async keyword. For any new development work, it is recommended that you use HttpClient. It has a number of advantages over WebClient , including more configuration options and it facilitates easier mocking and testing. However, it does have some disadvantages, such as the lack of built-in progress reporting.
In this article, I have covered the two main ways of downloading files using C and the. WebClient makes it really easy to download files, with its high-level API and it is available regardless of what. NET version you are targeting. Use HttpClient whenever you need more control and as the recommended option for new development. Yes, add me to your mailing list. This site uses Akismet to reduce spam.
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