topic Re: Look-up Selected Attribute Field Error in ArcGIS Pro SDK Questions

Look-up Selected Attribute Field Error

ThiPham12 — Tue, 22 Feb 2022 04:34:04 GMT

I am trying to return a list of selected feature attribute field, "mukey" from a feature class, "MUPOLYGON". I tried to look-up the mukey using the GetTable() method and creating a mukey list. However, I am getting an error that says cannot convert a Task to a string parameter when I tried to use the mukey list as a parameter for another method. I have the following questions:

1. What is a light weight method to obtain a mukey list from the selected feature field, mukey?

2. How do I resolve the conversion error?

public async Task LookupMukey()
{
var mukeys = new List<string>();
var MV = MapView.Active;
int mukeyCount = 0;
var SelectionLayer = MV.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().Where(fl => fl.Name.Contains("SelectionLayer")).FirstOrDefault();

await QueuedTask.Run(() =>
{
using (var SelectionTable = SelectionLayer.GetTable())
{
using (var rowCursor = SelectionTable.Search())
{
while (rowCursor.MoveNext())
{
using (Row row = rowCursor.Current)
{
var mukey = Convert.ToString(row["mukey"]);
mukeys.Add(mukey);
mukeyCount++;
}
}
}
}
return mukeys;
});
}

Using the mukey list as a parameter for another method:

Process.ChorizonData(mukeys,"awc_l", "awc_r", "awc_h", inputPath); //error occurs here at mukey

Thanks for your help!

Re: Look-up Selected Attribute Field Error

GKmieliauskas — Tue, 22 Feb 2022 06:14:33 GMT

Hi,

Your function must be like this :

public async Task<List<string>> LookupMukey() { var mukeys = new List<string>(); var MV = MapView.Active; int mukeyCount = 0; var SelectionLayer = MV.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().Where(fl => fl.Name.Contains("SelectionLayer")).FirstOrDefault(); await QueuedTask.Run(() => { using (var SelectionTable = SelectionLayer.GetTable()) { using (var rowCursor = SelectionTable.Search()) { while (rowCursor.MoveNext()) { using (Row row = rowCursor.Current) { var mukey = Convert.ToString(row["mukey"]); mukeys.Add(mukey); mukeyCount++; } } } } }); return mukeys; }

And call to function:

var mukeys = await LookupMukey();

Re: Look-up Selected Attribute Field Error

ThiPham12 — Tue, 22 Feb 2022 16:47:24 GMT

Thanks for your help Gintautas! When I tried to call the function, I am getting an error that says, "CS4034: The await operator can only be used with an async lambda expression. Consider marking this lambda expression with the async modifier." Where do I add the async modifier to the lambda expression?

Is this right? await QueuedTask.Run(async() =>... //error: lack await operator

Re: Look-up Selected Attribute Field Error

GKmieliauskas — Tue, 22 Feb 2022 17:08:41 GMT

You can add "async" to "var mukeys = await LookupMukey();" calling method like this:

public async voif Your_Method() { var mukeys = await LookupMukey(); }

or change LookupMukey method calling to:

var mukeys = LookupMukey().Result;

Re: Look-up Selected Attribute Field Error

tzz_12 — Sat, 26 Feb 2022 22:41:36 GMT

Hi Gintautas,

What if I am calling the LookupMukey method in a ICommand event handler? How should I call the LookupMukey()? Please see the example below:

//within a public ICommand CmdRun binded to a Run button

AllProcesses Process = new AllProcesses();

var mukeys = await Process.LookupMukey(); //error occurs here

//codes below - calling multiple methods and passing the list of mukeys as one of the parameters

Thanks for your help!

Re: Look-up Selected Attribute Field Error

GKmieliauskas — Tue, 01 Mar 2022 13:32:28 GMT

Hi,

If I understand right, it must be like this:

protected XViewModel() { _CommandX = new RelayCommand(() => CmdX(), true); } private ICommand _CommandX; public ICommand CommandX { get { return _CommandX; } } /// <summary> /// Execute the X command /// </summary> private async void CmdX() { AllProcesses Process = new AllProcesses(); var mukeys = await Process.LookupMukey(); //codes below - calling multiple methods and passing the list of mukeys as one of the parameters } // or private void CmdX() { AllProcesses Process = new AllProcesses(); var mukeys = Process.LookupMukey().Result; //codes below - calling multiple methods and passing the list of mukeys as one of the parameters }