Nested using statements in C#

The preferred way to do this is to only put an opening brace { after the last using statement, like this:

using (StreamReader outFile = new StreamReader(outputFile.OpenRead()))
using (StreamReader expFile = new StreamReader(expectedFile.OpenRead())) 
{
    ///...
}

If the objects are of the same type you can do the following

using (StreamReader outFile = new StreamReader(outputFile.OpenRead()), 
                    expFile = new StreamReader(expectedFile.OpenRead()))
{
    // ...
}

When the IDisposables are of the same type, you can do the following:

 using (StreamReader outFile = new StreamReader(outputFile.OpenRead()), 
     expFile = new StreamReader(expectedFile.OpenRead()) {
     // ...
 }

The MSDN page on using has documentation on this language feature.

You can do the following whether or not the IDisposables are of the same type:

using (StreamReader outFile = new StreamReader(outputFile.OpenRead()))
using (StreamWriter anotherFile = new StreamReader(anotherFile.OpenRead()))
{ 
     // ...
}