Are optional params available for the Compact Framework?

问题

I need to get a list of all files on a handheld device whose names fit a certain pattern, such as "ABC.XML"

I adapted code from here (Hernaldo's answer), like so:

public static List<string> GetXMLFiles(string fileType, string dir)
{
    string dirName = dir; // call it like so: GetXMLFiles("ABC", "\\");  <= I think the double-whack is what I need for Windows CE device...am I right?
    var fileNames = new List<String>();
    try
    {
        foreach (string f in Directory.GetFiles(dirName))
        {
            if ((f.Contains(fileType)) &&  (f.Contains(".XML")))
            {
                fileNames.Add(f);
            }
        }
        foreach (string d in Directory.GetDirectories(dirName))
        {
            GetXMLFiles(fileType, d);
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
    return fileNames;
}

...but each time the method recursively calls itself (in the GetDirectories() loop), I'm passing the same old first arg. Is it possible (in Compact Framework) to do something like this instead:

public static List<string> GetXMLFiles(optional string fileType, string dir)
{
        . . .        
        foreach (string d in Directory.GetDirectories(dirName))
        {
            GetXMLFiles(dir = d);
        }
        . . .

UPDATE

According to Habib, this should work (new "try" section):

try
{
    string filePattern = string.Format("*{0}*.XML", fileType);
    foreach (string f in Directory.GetFiles(dirName, filePattern))
    {
        fileNames.Add(f);
    }
    foreach (string d in Directory.GetDirectories(dirName))
    {
        GetXMLFiles(fileType, d);
    }
}

Ja?

UPDATE 2

This goes along with my second response to Alan's comment below:

const string EXTENSION = ".XML";
. . .
try
{
    foreach (string f in Directory.GetFiles(dirName))
    {
        string ext = Path.GetExtension(f);
        string fileNameOnly = Path.GetFileNameWithoutExtension(f);
        if ((ext.Equals(EXTENSION, StringComparison.Ordinal)) && (fileNameOnly.Contains(fileType)))
        {
            fileNames.Add(f);
        }
    }
    foreach (string d in Directory.GetDirectories(dirName))
    {
        GetXMLFiles(fileType, d);
    }
}

回答1:

Optional parameters are a feature of .NET 4.0, so you won't be able to use them. The typical solution to this with a recursive function is to create two overloads for your method with different parameters.

For example,

BinarySearch(array a);
{
  BinarySearch(a, -1, array.Length);
} 

BinarySearch(array, low, high)
{
   //code to update low high
   return BinarySearch(array, low, high);
}

In this case, the method which kicks off the recursion has a slightly different signature. You could do the same.