sharpsvn diff - how to ignore spacing / whitespaces

Question

I'm using the sharpSVN API to among others to find out about changes in a repository. Therefore I use the method Diff of the SVNClient class in the following way:

using (SvnClient client = new SvnClient())
{
    MemoryStream diffResultStream = new MemoryStream();
    client.Diff(SvnTarget.FromString(svnDir), new SvnRevisionRange(SvnRevision.Head, SvnRevision.Working), diffResultStream); 

...
}

I already tried to use the SvnDiffArgs attribute, but didn't succeed:

SvnDiffArgs da = new SvnDiffArgs();
da.DiffArguments.Add("-x -u -b -w");
client.Diff(..., da, diffResultStream);

I also found the SvnIgnoreSpacing.IgnoreAll enum, but don't have a clue what to do with it. The documentation is quite poor. Using Google I only found it beeing used in conjunction with the Blame method.

Can anybody help me how to make that very same diff to ignore whitespaces?

Many thanks in advance