How to query a data source with the Common Data Source API

Summary

This topic shows how to use the generic Common Data Source application programming interface (API) interfaces in the Web Application Developer Framework (ADF) to query a feature layer within a map resource.

Querying a data source with the Common Data Source API

This topic assumes that a MapResourceManager and Map (named Map1) are available in the current scope and that a layer in a map resource has the following properties:

An ID value of "states"
A field named STATE_NAME that contains attributes that start with 'N'
The same attributes have spatial features within the geographic extent (–120, 30) to (–100, 50) in decimal degrees

The map resource type is non-specific; therefore, any data source implementation that is part of the Web ADF and supports queries can be used (for example, ArcIMS or ArcGIS for Server). An initial test for query support is included. The results for the Query method are returned in a standard .NET DataTable object (System.Data.DataTable).

See the following code example:

[C#]


        foreach (ESRI.ArcGIS.ADF.Web.DataSources.IGISFunctionality gisFunctionality in
    Map1.GetFunctionalities())
{
    ESRI.ArcGIS.ADF.Web.DataSources.IGISResource gisResource =
        gisFunctionality.Resource;
    bool supported = gisResource.SupportsFunctionality(typeof
        (ESRI.ArcGIS.ADF.Web.DataSources.IQueryFunctionality));

    if (supported)
    {
        ESRI.ArcGIS.ADF.Web.DataSources.IQueryFunctionality queryFunctionality = 
            (ESRI.ArcGIS.ADF.Web.DataSources.IQueryFunctionality)
            gisResource.CreateFunctionality(typeof
            (ESRI.ArcGIS.ADF.Web.DataSources.IQueryFunctionality), null);

        string[] layerIDs = null;
        string[] layerNames = null;
        queryFunctionality.GetQueryableLayers(null, out layerIDs, out layerNames);

        ESRI.ArcGIS.ADF.Web.SpatialFilter spatialFilter = new
            ESRI.ArcGIS.ADF.Web.SpatialFilter();
        spatialFilter.ReturnADFGeometries = true;
        spatialFilter.MaxRecords = 1000;

        spatialFilter.WhereClause = "STATE_NAME LIKE 'N%'";

        ESRI.ArcGIS.ADF.Web.Geometry.Envelope adfEnvelope = new
            ESRI.ArcGIS.ADF.Web.Geometry.Envelope( - 120, 30,  - 100, 50);
        spatialFilter.Geometry = adfEnvelope;

        string activeLayerString = "states";
        System.Data.DataTable queryResultsDataTable = null;
        for (int i = 0; i < layerNames.Length; i++)
        {
            if (layerNames[i].Equals(activeLayerString))
            {
                queryResultsDataTable = queryFunctionality.Query
                    (gisFunctionality.Name, layerIDs[i], spatialFilter);
                break;
            }
        }
    }
}

[VB.NET]


        For Each gisFunctionality As ESRI.ArcGIS.ADF.Web.DataSources.IGISFunctionality In Map1.GetFunctionalities()
    Dim gisResource As ESRI.ArcGIS.ADF.Web.DataSources.IGISResource = gisFunctionality.Resource
    Dim supported As Boolean = gisResource.SupportsFunctionality(GetType(ESRI.ArcGIS.ADF.Web.DataSources.IQueryFunctionality))
    
    If supported Then
        Dim queryFunctionality As ESRI.ArcGIS.ADF.Web.DataSources.IQueryFunctionality = CType(gisResource.CreateFunctionality (GetType(ESRI.ArcGIS.ADF.Web.DataSources.IQueryFunctionality), Nothing), ESRI.ArcGIS.ADF.Web.DataSources.IQueryFunctionality)
        
        Dim layerIDs As String() = Nothing
        Dim layerNames As String() = Nothing
        queryFunctionality.GetQueryableLayers(Nothing, layerIDs, layerNames)
        
        Dim spatialFilter As ESRI.ArcGIS.ADF.Web.SpatialFilter = New ESRI.ArcGIS.ADF.Web.SpatialFilter()
        spatialFilter.ReturnADFGeometries = True
        spatialFilter.MaxRecords = 1000
        
        spatialFilter.WhereClause = "STATE_NAME LIKE 'N%'"
        
        Dim adfEnvelope As ESRI.ArcGIS.ADF.Web.Geometry.Envelope = New ESRI.ArcGIS.ADF.Web.Geometry.Envelope( -120, 30, -100, 50)
        spatialFilter.Geometry = adfEnvelope
        
        Dim activeLayerString As String = "states"
        Dim queryResultsDataTable As System.Data.DataTable = Nothing
        Dim i As Integer = 0
        Do While i < layerNames.Length
            If layerNames(i).Equals(activeLayerString) Then
                queryResultsDataTable = queryFunctionality.Query(gisFunctionality.Name, layerIDs(i), spatialFilter)
                Exit Do
            End If
            i + = 1
        Loop
    End If
Next gisFunctionality