topic Re: Attribute Query Task Question in ArcGIS API for Silverlight Questions

Attribute Query Task Question

ChristineZeller — Mon, 01 Nov 2010 17:53:55 GMT

I'm trying to implement the Attribute Query example from the SDK and I can get it working on my machine "as is" but when I change over to a layer that I'm servering it doesn't work. Also if I change the example to just use a different field like STATE_ABBR instead of STATE_NAME I have the same problem....it breaks! Am I missing a change?

Thanks
Christine

Re: Attribute Query Task Question

JenniferNery — Mon, 01 Nov 2010 18:01:14 GMT

When you say "it breaks", what error message do you see? Have you tried to use Fiddler to see where it possibly fails?

Re: Attribute Query Task Question

ChristineZeller — Mon, 01 Nov 2010 19:31:17 GMT

Jennifer, thanks for the reply! Yea it fires when I use the State_Name but like I said if I just switch it to a different field like STATE_ABBR (just two easy changes in the code behind). It never returns the query and/or zooms to the feature. Here's the last fiddler.

I've attached a screen shot of my last fiddler result.

It seems like there is some little stupid change I'm missing. Do I need to change the WHERE? I not really sure what the where is stating "query.Where = "1=1";"

Christine

Re: Attribute Query Task Question

JenniferNery — Sat, 11 Dec 2021 07:02:14 GMT

Oh I see what the problem is now. In this sample http://help.arcgis.com/en/webapi/silverlight/samples/start.htm#AttributeQuery (if you are using this), the query OutFields only include "STATE_NAME".

The service that it's using is http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/ESRI_Census_USA/MapServer/5 and "STATE_ABBR", while it is a valid field, is not included in the OutFields. You can update this line

query.OutFields.AddRange(new string[] { "STATE_NAME", "STATE_ABBR" });
//or simply use * to return all fields -- query.OutFields.Add("*");

Re: Attribute Query Task Question

ChristineZeller — Sat, 11 Dec 2021 07:02:16 GMT

Oh I see what the problem is now. In this sample http://help.arcgis.com/en/webapi/silverlight/samples/start.htm#AttributeQuery (if you are using this), the query OutFields only include "STATE_NAME".

The service that it's using is http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/ESRI_Census_USA/MapServer/5 and "STATE_ABBR", while it is a valid field, is not included in the OutFields. You can update this line
query.OutFields.AddRange(new string[] { "STATE_NAME", "STATE_ABBR" });
//or simply use * to return all fields -- query.OutFields.Add("*");

Jennifer, thanks again for the replies. I am using the sample you pointed to. I was just changing the code like:

// Specify fields to return from initial query
//query.OutFields.AddRange(new string[] { "STATE_ABBR" });

If I try this instead:

query.OutFields.AddRange(new string[] { "STATE_NAME", "STATE_ABBR" });

I get the same results...no return...just sits there

If I try:
query.OutFields.Add("*");

I get the same.

The only other thing I'm changing is

 if ((args.UserState as string) == "initial")
            {
                // Just show on initial load
                QueryComboBox.Items.Add("Select...");

                foreach (Graphic graphic in args.FeatureSet.Features)
                {
                    QueryComboBox.Items.Add(graphic.Attributes["STATE_ABBR"].ToString());


                }

                QueryComboBox.SelectedIndex = 0;
                return;
            }

Re: Attribute Query Task Question

JenniferNery — Sat, 11 Dec 2021 07:02:19 GMT

Looking at how the Query is formed, it uses Text property which checks against the layer's DisplayField http://help.arcgis.com/en/webapi/silverlight/apiref/ESRI.ArcGIS.Client~ESRI.ArcGIS.Client.Tasks.Query~Text.html

In the given layer, DisplayField is STATE_NAME, therefore the query with STATE_ABBR does not return any results.
http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/ESRI_Census_USA/MapServer/5

I will update Where property instead of Text property in the SelectionChanged event handler. http://help.arcgis.com/en/webapi/silverlight/apiref/ESRI.ArcGIS.Client~ESRI.ArcGIS.Client.Tasks.Query~Where.html

 query.Where = string.Format("STATE_ABBR = '{0}'", QueryComboBox.SelectedItem);

Re: Attribute Query Task Question

ChristineZeller — Mon, 01 Nov 2010 23:29:24 GMT

Jennifer,

Very cool! It is now coming clear and with your help I have the sample working. I'm still slightly confused on adding another parameter to my query. I can't seem to get the syntax down would I do something like:

query.Where = string.Format("STATE_ABBR = '{0}'", QueryComboBox.SelectedItem) and MED_AGE < 46;

or would it go up in the initialize like

query.Where = "MED_AGE < 33" and "MED_AGE_M > 32";

Both syntax are giving me errors.

You tired to point me in the right direction with this:
http://forums.arcgis.com/threads/16119-Attribute-Query-on-Muitiple-fields

Re: Attribute Query Task Question

JenniferNery — Sat, 11 Dec 2021 07:02:22 GMT

Have you used string.Format()? Here's some documentation on how it is used. http://msdn.microsoft.com/en-us/library/system.string.format(v=VS.100).aspx

You can update the Where to the following code:

int min = 32, max = 33;
query.Where = string.Format("STATE_ABBR = '{0}' and MED_AGE < {1}and MED_AGE_M > {2}", QueryComboBox.SelectedItem, min, max);

The best way to test if you are constructing a good SQL Where clause is to try it out on the browser first, by clicking on "Query Layer" link underneath the layer URL.

Re: Attribute Query Task Question

ChristineZeller — Wed, 03 Nov 2010 19:28:17 GMT

Jennifer,

Thanks a bunch for your help! I really apprecaite it.....you rock! I was hoping to ask another question.

So the for loop that is populating the combo box is running on a field that doesn't have unique vales for each record.....in the sdk example it is populating state names and each state has a unique name but I'm populating it with call types and the call types repeat.

So my questing is how can I eliminate duplications (ex. Call Type = Traffic Stop is listed 15 times in the list and I only want to list it once.

                foreach (Graphic graphic in args.FeatureSet.Features)
                {
                    TypeDescComboBox.Items.Add(graphic.Attributes["TYPEDESC"].ToString());
                }

thanks
Christine.

Re: Attribute Query Task Question

JenniferNery — Sat, 11 Dec 2021 07:02:24 GMT

You can use Distinct() from System.Linq and set your ComboBox ItemsSource property, provided that it does not already contain items.

TypeDescComboBox.ItemsSource = (from g in args.FeatureSet.Features
            select g.Attributes["TYPEDESC"]).Distinct();

This is just one way, you can also use a dictionary or list to temporarily hold the attribute values and check whether the attribute value already exist before adding to your ComboBox.

Running Query for a field for repeated numbers

ChaitanyaPathak — Sat, 06 Nov 2010 22:45:42 GMT

Hello Everyone,
I am new to ArcGIS and would like to know if there is any way where in I can query the attribute table (particularly a field) which has number for example (1,1,2,2,2,4,4,4,4,4,4,5,6,6,6) and I want to know all the fields which has more than one repetation of numbers. In above example I really don't care about number 5 because its occuring only once. Reponse in this regard would be highly appreciated.
Thank you

Re: Attribute Query Task Question

JenniferNery — Sat, 11 Dec 2021 07:02:27 GMT

The Where property of a Query is any legal SQL Where clause as been said here: http://help.arcgis.com/en/webapi/silverlight/apiref/ESRI.ArcGIS.Client~ESRI.ArcGIS.Client.Tasks.Query~Where.html

So I don't think you can get repeating values by updating the query alone. You can probably use System.Linq query on the results.

Please don't hold me accountable for the syntax 🙂 but I think it's something like this:

var repeatingValues = from g in args.FeatureSet.Features
group g by g.Attributes["FieldName"] into f
where f.Count() > 1
select f.Key;