This is where I ended up...
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public async void MnlSrchCmbobx_SelectionChangeCommitted(object sender, EventArgs e)
{
var attfn = MnlSrchCmbobx.Text; //string choice from combobox (search field)
Form1.GVar.ms_attfn = attfn; //string to global variable
await ActMap(); //active map checker
Map map = MapView.Active.Map;
var srch_lyr = map.FindLayers(lyr).FirstOrDefault() as FeatureLayer; //layer locator from "lyr" in activemap TOC
await QueuedTask.Run(() =>
{
TableDefinition srch_FCD = srch_lyr.GetTable().GetDefinition(); //table definition of featurelayer
var Find_Fld = srch_FCD.FindField(attfn); //find the search field index
var Get_Flds = srch_FCD.GetFields(); //get the readonly collection of fields from the table
Field ms_field = Get_Flds.ElementAt(Find_Fld); //Field object: via search field index from collection
var FldTp = ms_field.FieldType.ToString(); //get fieldtype as a string
Form1.GVar.ms_v_datatype = FldTp; //assign fieldtype to global variable
});
AsetSrchFldDTLbl.Text = Form1.GVar.ms_v_datatype; //test output on sub-form to a label.
}
Thanks, Rich and Uma.