topic Re: Checking to see if A field has a null value in ArcGIS API for Silverlight Questions

Checking to see if A field has a null value

DavidAshton — Mon, 16 Jan 2012 16:16:42 GMT

I have created a graphic layer by a attribute/spatial selection tools. I've created a graphic layer named graphicLayer. I want to check to see if a field (AsBuiltDate) is null but I'm having trouble with the code/syntax. Can someone help?

if (graphicsLayer.Graphics.Attributes["AsBuiltDate"] == "NULL")                 {                 }

Thanks
Dave

Re: Checking to see if A field has a null value

JMcNeil — Sat, 11 Dec 2021 20:58:43 GMT

Something like this:

   foreach (Graphic graphic in graphicsLayer.Graphics)
                    {
                        if (graphic.Attributes["AsBuiltDate"] == "Null")
                        {
//DO SOMETHING IF NULL
}
}

JAY

Re: Checking to see if A field has a null value

DavidAshton — Sat, 11 Dec 2021 20:58:46 GMT

Thanks Jay...that got me halfway there. The rest wanted something like "AsBuilt_Date is NULL" but is was erroring with the null so I did something like graphics1.Attributes["AsBuilt_Date"] is Nullable

my code doesn't crash but it is not working entirely. I'm trying loop there several graphics and only a few records are null here's what I'm trying to do:

 if (PieChartLayers.SelectedIndex == 3)
                {
                      //      PieChart.Title = "ASBUILT DATE"; AsBuiltDate

                    foreach (Graphic graphics1 in graphicsLayer.Graphics)
                    {

                        if (graphics1.Attributes["AsBuilt_Date"] is Nullable)
                           


                        {



                            Groups1 = graphicsLayer.Graphics.GroupBy(graphic => (DateTime)graphic.Attributes["AsBuilt_Date"],
                                            (date, graphics) => new AttributeGroup
                                           {

                                               Key = date.ToString(),
                                               //   GISDATE = DateTime.ParseExact(date.ToString(), "yyyyMMdd", System.Globalization.CultureInfo.CurrentCulture),                            
                                               // Key = String.Format("{0:####-##-##}", date),
                                               Count = graphics.Count(),
                                               //    Sum = graphics.Select(g => (int16)g.Attributes["DOW"]).Sum(),
                                               Graphics = graphics
                                           }).OrderBy(group => group.Key).ToArray();

                        }
                    }
                }

My code doesn't fail now but if doesn't report back the/graph the none null fields. Maybe I need to assign the null records a value?? Thanks for the help. Anymore would be much appreciated.

Dave

\

Re: Checking to see if A field has a null value

JenniferNery — Wed, 18 Jan 2012 16:23:46 GMT

You can use query.Where = "NOT (description is NULL)".

http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Fire/Sheep/FeatureServer/0/query?objectIds=&where=not+%28description+is+NULL%29&time=&geometry=&geometryType=esriGeometryEnvelope&inSR=&spatialRel=esriSpatialRelIntersects&relationParam=&outFields=*&returnGeometry=true&outSR=&returnIdsOnly=false&f=html

Or if you have already retrieved all features and want to filter the results via client API, you can use linq Query, you can do the following in QueryTask.ExecuteCompleted event handler:

var nonNullValues = from f in e.FeatureSet.Features  where f.Attributes["description"] != null  select f;