Best way of making an argument optional for a C# webmethod

Question

What is the best way of supporting optional data passed to a C# function?

I have web service function in .Net which defines 5 arguments:

[WebMethod]
    public string UploadFile( string wsURL
        , byte[] incomingArray
        , string FileName
        , string RecordTypeName
        , MetaData[] metaDataArray)

The code of this function is not too long (but not trivial either) and there is only one place in the the function where I perform this test if there is any MetaData[] to be processed:

        if (metaDataArray.Length > 0)
        {
            Update update = BuildMetaData(metaDataArray);
            treq2.Items = new Operation[] { sru, cin, update, fetch};
        }
        else
        {
            treq2.Items = new Operation[] { sru, cin, fetch};
        }

I needed a quick and dirty version of the above which only takes 4 arguments (i.e. no "Metadata" array as a final argument) so I cloned the whole function and removed the IF-ELSE block refering to metadata. Ugly I know.

[WebMethod]
    public string UploadFileBasic( string wsURL
        , byte[] incomingArray
        , string FileName
        , string RecordTypeName)

Now I want to do things better and I am looking for advice on the best way to support this. I do not want to burden the client program with creating an empty array as a 5th parameter...I want to have my web service functions to be smart enough to handle this optional data. Thanks.

Answer 1

private static readonly MetaData[] EmptyMetaData = new MetaData[0];

[WebMethod]
public string UploadFile(string wsURL
    , byte[] incomingArray
    , string fileName
    , string recordTypeName)
{
    return UploadFile(wsURL, incomingArray, fileName, recordTypeName, EmptyMetaData)
}

Answer 2

[WebMethod]
    public string UploadFileBasic( string wsURL
        , byte[] incomingArray
        , string FileName
        , string RecordTypeName)
{
    return UploadFile(wsURL, incomingArray, FileName, RecordTypeName, new MetaData[0]);
}

Then the UploadFile method handles everything, but you're able to expose two interfaces depending on what the consumer wants.

Answer 3

Change your check in the method that takes 5 arguments to (note, that you should be checking if the value is null anyway).

    if (metaDataArray != null && metaDataArray.Length > 0)
    {
        Update update = BuildMetaData(metaDataArray);
        treq2.Items = new Operation[] { sru, cin, update, fetch };
    }
    else
    {
        treq2.Items = new Operation[] { sru, cin, fetch};
    }

Then, simply have your 4 argument version call the 5 argument version internally with the metaDataArray argument null.

[WebMethod]
public string UploadFileBasic( string wsURL,
                               byte[] incomingArray,
                               string FileName,
                               string RecordTypeName)
{
    return UploadFile( wsUrl, incomingArray, fileName, RecordTypeName, null );
}

Answer 4

How about putting all the arguments including the MetaData Array into a single class and use it as argument to the web service:

public class UploadFileAgrument 
{
  public string wsURL;
  public byte[] incomingArray;
  public string FileName;
  public string RecordTypeName;
  public MetaData[] metaDataArray;
}

[WebMethod]
public string UploadFile(UploadFileAgrument fileToUpload)
{
  if(fileToUpload.metaDataArray!=null && metaDataArray.Length > 0)
  {
  }
  else
  {
  }  
}