// Pick K random clusters
while(clusterNumbers.Count < clusterCount)
{
    clusterNumber = random.Next(0, rowCount-1);
    if (!clusterNumbers.Contains(clusterNumber)) // <----- Should check if a similar datapoint is already in there instead of clusternumber
    {
        cluster = new Cluster();
        clusterNumbers.Add(clusterNumber);
        dataPoint = new double[fieldCount];

        for (int field = 0; field < fieldCount; field++)
        {
            dataPoint.SetValue((data[clusterNumber, field]),field);   
        }

        cluster.Add(dataPoint);
        clusters.Add(cluster);
    }
}

Attached please see the zip file what you need. Bless.

谢谢