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Attribute Query Task Question

ChristineZeller

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

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JenniferNery

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;

ChaitanyaPathak

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

JenniferNery

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.

ChristineZeller

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.

JenniferNery

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.

ChristineZeller

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

JenniferNery

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);

ChristineZeller

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;
            }

JenniferNery

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("*");

ChristineZeller

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

AttCapFid.PNG

JenniferNery

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

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