When you think ASP, think...
Recent Articles
All Articles
ASP.NET Articles
Message Board
Related Web Technologies
User Tips!
Coding Tips

Sample Chapters
Commonly Asked Message Board Questions
JavaScript Tutorials
MSDN Communities Hub
Official Docs
Stump the SQL Guru!
XML Info
Author an Article
ASP ASP.NET ASP FAQs Message Board Feedback

The 4 Guys Present: ASPFAQs.com

Jump to a FAQ
Enter FAQ #:
..or see our 10 Most Viewed FAQs.

4GuysFromRolla.com : ASP FAQS : XML


In ASP.NET, how can I create an XmlDocument instance from an XML string? Similarly, given an XML string, how can I display the data in a data Web control?

[Print this FAQ]

Answer: Loading XML Strings Into XML Objects
The XmlDocument class - and related classes, such as XmlTextReader, XPathDocument, and so on - have a variety of constructor overloads or provide means for XML data to be loaded in a number of ways. These ways, while not common to all XML-related classes in the .NET Framework, but found in most, are:

* Specifying a string that is a URL or file path of an XML file
* Passing in a stream instance that contains the XML data
* Passing in a TextReader instance that contains the XML data

What many developers might think is missing from the list is, being able to just pass in a string of XML. That is, one might want to create an XmlDocument instance like do:

XmlDocument xmlDoc = new XmlDocument();

This approach can be useful if you are needing to load an XmlDocument (or other XML-related object) based on the XML returned by a Web service or some component. However, none of the XML-related classes in the .NET Framework accept a raw XML string for initialization.

(NOTE: The XmlDocument class has the LoadXml() method that will load an XmlDocument from XML string data; however, if you want to do any validation, this method is not an option. Also, the other XML-related classes - XmlTextReader, XPathDocument, and so on - do not expose such a method.)

One approach would be to take the XML string, dump it to a temporary file, and then speicfy the file's path in the Load() method or the constructor. However, this approach is unnecessarily inefficient and leaves a mess of temporary files.

The ideal approach is to load the data into a TextReader. We can then pass the TextReader instance into the appropriate XML class instance. If you look at the TextReader class's technical documentation, you'll find that two classes are derived from the TextReader class: StreamReader and StringReader. Checking out the StringReader's technical documentation you'll see that a StringReader instance can be created by passing in the string into its constructor.

Since these XML-related classes will accept a TextReader, we can simply create a StringReader populated with the XML data in string form, and then pass in the StringReader. The following code shows how to load string XML data into an XmlDocument instance:

StringReader sr = new StringReader("<book><title>...");

XmlDocument xmlDoc = new XmlDocument();

Displaying an XML String in a Data Web Control
Displaying an XML string in a data Web control, such as the DataGrid, DataList, or Repeater, is easy to do once you have loaded a DataSet with the XML data. The DataSet class contains a ReadXml() method, which like XML-related classes we looked at earlier, accepts:

* Specifying a string that is a URL or file path of an XML file
* Passing in a stream instance that contains the XML data
* Passing in a TextReader instance that contains the XML data

Again, we are faced with the same problem as before if what we have is not a URL or file with the XML data, but a string of XML data. Again, the solution is to use a StringReader to load the XML string data, and then pass in this StringReader into the DataSet's ReadXml() method. Finally, the DataSet can then be bound to the data Web control.

The following source code demonstrates how this would be done:

StringReader sr = new StringReader("<book><title>...");
DataSet ds = new DataSet();


myDataGrid.DataSource = ds;

For a more thorough discussion on this, be sure to read Anthony Hart's DataGrids, DataSets, and XML Strings.

Happy Programming!

FAQ posted by Scott Mitchell at 10/16/2003 12:34:42 PM to the XML category. This FAQ has been viewed 73,586 times.

Do you have a FAQ you'd like to suggest? Suggestions? Comments? If so, send it in! Also, if you'd like to be a FAQ Admin (creating/editing FAQs), let me know! If you are looking for other FAQs, be sure to check out the 4Guys FAQ and Commonly Asked Messageboard Questions!

Most Viewed FAQs:

1.) How can I format numbers and date/times using ASP.NET? For example, I want to format a number as a currency. (761643 views)
2.) I am using Access and getting a 80004005 error (or a [Microsoft][ODBC Microsoft Access Driver] The Microsoft Jet database engine cannot open the file '(unknown)' error) when trying to open a connection! How can I fix this problem? (207777 views)
3.) How can I convert a Recordset into an array? Also, how can I convert an array into a Recordset? (202549 views)
4.) How can I quickly sort a VBScript array? (196039 views)
5.) How can I find out if a record already exists in a database? If it doesn't, I want to add it. (156019 views)
6.) How do I display data on a web page using arrays instead of Do...While...MoveNext...???... (152331 views)
7.) When I get a list of all files in a directory via the FileSystemObject, they aren't ordered in any reasonable way. How can I sort the files by name? Or by size? Or by date created? Or... (140381 views)
8.) For session variables to work, must the Web visitor have cookies enabled? (110162 views)
9.) Can I send emails without using CDONTS? (107083 views)
10.) How can I take the result of a SELECT...MULTIPLE or a group of same-named checkboxes and turn it into a query? That is, if the user selects 3 answers, how can I construct a query that looks for all 3? (106308 views)
Last computed at 9/17/2007 3:22:00 AM

ASP.NET [1.x] [2.0] | ASPMessageboard.com | ASPFAQs.com | Advertise | Feedback | Author an Article