It actually was a problem with the case sensitivity of the where clause, and I've got that part fixed. Now, however, none of the features will draw.
private void QueryTask_ExecuteCompleted(object sender, QueryEventArgs args)
{
GraphicsLayer graphicsLayer = MapApplication.Current.Map.Layers["MyGraphicsLayer"] as GraphicsLayer;
FeatureSet featureSet = args.FeatureSet;
if (featureSet.Features.Count > 0)
{
foreach (Graphic resultFeature in featureSet.Features)
{
resultFeature.Symbol = YellowLine;
graphicsLayer.Graphics.Add(resultFeature);
}
MessageBox.Show(featureSet.Features.Count.ToString() + " lines found");
}
}