C-Sharp .Net Xml Xslt Stream

Converting `StreamReader` to `XmlReader` in .Net 2.0/C#

In the world of .NET programming, working with XML files is a common task, especially when dealing with datasets. If you’ve ever found yourself attempting to convert a StreamReader into an XmlReader and hitting a wall, you’re not alone.

In this blog post, we’ll break down a common problem faced during this conversion and explore how to effectively address it.

The Problem

You are trying to convert a .NET DataSet into an XML stream, apply an XSL transformation in memory, and write the modified XML to a new file. However, difficulties arise when creating an XmlReader from a StreamReader that appears to have no data.

Here’s a brief overview of your attempted code:

BufferedStream stream = new BufferedStream(new MemoryStream());
DataSet ds = new DataSet();
da.Fill(ds);
ds.WriteXml(stream);

StreamReader sr = new StreamReader(stream, true);
stream.Position = 0; // Position reset for reading

XmlReader reader = XmlReader.Create(sr, null); // Issue occurs here

The main problem is the XmlReader being created without recognizing any data from the StreamReader.

Understanding the Cause

The key issues noted in the code:

Stream Positioning: The position of the stream must be reset to enable StreamReader to read from the beginning of the stream.
Stream Closure: Proper handling of the stream, including closing or flushing it post-writing, is crucial for data integrity.

The Solution

Here’s a straightforward approach to resolve the issues with your existing code:

Step 1: Reset the Stream Position

Before reading from the StreamReader, ensure that the position of the BufferedStream is reset. This can be achieved with the Seek method or setting the Position property directly.

Step 2: Correctly Create the XmlReader

Create a new XmlReader after ensuring that the stream is appropriately positioned to the start.

Step 3: Implement the Working Code

Here’s a working example of how to perform these operations:

BufferedStream stream = new BufferedStream(new MemoryStream());
stream.Write(Encoding.ASCII.GetBytes("<xml>foo</xml>"), 0, "<xml>foo</xml>".Length);
stream.Seek(0, SeekOrigin.Begin); // Important: Reset stream position

using (StreamReader sr = new StreamReader(stream))
{
    using (XmlReader reader = XmlReader.Create(sr))
    {
        while (reader.Read())
        {
            Console.WriteLine(reader.Value);
        }
    }
}

Explanation of the Code:

Writing to Stream: Here, we’re writing a simple XML structure to the stream.
Resetting Position: By using Seek(0, SeekOrigin.Begin), we ensure our stream reader starts from the beginning.
Reading with XmlReader: The XmlReader.Create(sr) reads the XML, and we can now output its content.

Conclusion

By ensuring the proper handling of the stream and resetting it to the correct position, you can avoid the pitfalls encountered when converting a StreamReader to an XmlReader in .Net 2.0/C#. Handling XML in .NET can be straightforward if we pay close attention to our stream management.

Implement these changes, and you should see a marked improvement in your XML handling capabilities!

Converting StreamReader to XmlReader in .Net 2.0/C#