SPARQL results in WPF (binding DataGrid) -

i use dotnetrdf , display results query in wpf. function in viewmodel. have datatable use next in view.

        //results         sparqlresultset results;         datatable table;         //define remote endpoint         //use dbpedia sparql endpoint default graph set dbpedia         sparqlremoteendpoint endpoint = new sparqlremoteendpoint(new uri("http://dbpedia.org/sparql"), "http://dbpedia.org");          //make select query against endpoint         results = endpoint.querywithresultset("prefix dbo: <http://dbpedia.org/ontology/> prefix : <http://dbpedia.org/resource/> select ?film ?producername {    ?film dbo:director :andrzej_wajda .    ?film dbo:producer ?producername . }");         foreach (sparqlresult result in results)         {            console.writeline(result.tostring());         }          table = new datatable();         datarow row;          switch (results.resultstype)         {             case sparqlresultstype.variablebindings:                 foreach (string var in results.variables)                 {                     table.columns.add(new datacolumn(var, typeof(inode)));                 }                  foreach (sparqlresult r in results)                 {                     row = table.newrow();                      foreach (string var in results.variables)                     {                         if (r.hasvalue(var))                         {                             row[var] = r[var];                         }                         else                         {                             row[var] = null;                         }                     }                     table.rows.add(row);                 }                 break;             case sparqlresultstype.boolean:                 table.columns.add(new datacolumn("ask", typeof(bool)));                 row = table.newrow();                 row["ask"] = results.result;                 table.rows.add(row);                 break;              case sparqlresultstype.unknown:             default:                 throw new invalidcastexception("unable cast sparqlresultset datatable resultset has yet filled data , has no sparqlresultstype determines how cast datatable");         } 

in wpf use code:

<datagrid itemssource="{binding table}" autogeneratecolumns="true"/> 

binding work , dynamic created columns , datagrid, header. don't value of rows. in example there rows, without values.

where problem ? lot :)

this question not dotnetrdf other starting data sparql query how datagrid behaves when itemssource datatable , autogeneratecolumns used.

the basic problem datagrid not know how display arbitrary data types , generates datagridtextcolumn auto-generated columns. unfortunately supports string values or types explicit ivalueconverter applied afaik, doesn't call tostring() because conversions expected 2 way hence why see empty columns (thanks this question explaining this).

so getting values appropriately displayed requires create datatemplate our columns use. want use autogeneratecolumns need add handler autogeneratingcolumns event so:

<datagrid itemssource="{binding table}" autogeneratecolumns="true"           autogeneratingcolumn="autogeneratingcolumn" /> 

next need add implementation of event handler apply appropriate column type each auto-generated column so:

private void autogeneratingcolumn(object sender, system.windows.controls.datagridautogeneratingcolumneventargs e) {     if (e.propertytype != typeof (inode)) return;     datatabledatagridtemplatecolumn column = new datatabledatagridtemplatecolumn();     column.columnname = e.propertyname;     column.clipboardcontentbinding = e.column.clipboardcontentbinding;     column.header = e.column.header;     column.sortmemberpath = e.column.sortmemberpath;     column.width = e.column.width;     column.celltemplate = (datatemplate) resources["nodetemplate"];      e.column = column; } 

note use of special datatabledatagridtemplatecolumn type here, class answer binding wpf datagrid datatable using templatecolumns renamed more descriptive.

the reason can't use datagridtemplatecolumn directly when binding datatable template each column passed entire row rather specific column value need extend class in order bind specific column value our template formats actual inode value column in row , not whole row.

finally need define template we've referred in our xaml our columns appropriately formatted:

<window.resources>     <sparqlresultsdatagridwpf:methodtovalueconverter x:key="methodtovalueconverter" />     <datatemplate x:key="nodetemplate" datatype="rdf:inode">         <textblock text="{binding converter={staticresource methodtovalueconverter}, converterparameter='tostring'}"/>     </datatemplate> </window.resources> 

note i've defined value converter here, methodtovalueconverter taken answer of bind method in wpf? , allows take result of method call on arbitrary type , use our display value. here configuration of our template calls tostring() on underlying inode instances.

with these things implemented run example query , following in datagrid:

you can find code used @ https://bitbucket.org/rvesse/so-23711774

you can use basic approach construct more robust rendering of inode many visual bells , whistles see fit.

side notes

a couple of notes related answer, firstly have been easier produce if had posted minimal complete example of code rather partial xaml , code fragments.

secondly dotnetrdf sparqlresultset class has explicit cast datatable defined shouldn't need manually translate datatable unless want control structure of datatable e.g.

datatable table = (datatable) results;