Switch to using string instead of bool for checkbox values

WebCms/Models/LeafDataQuery.cs

@@ -1,4 +1,5 @@
-using System.ComponentModel.DataAnnotations;
+using System.ComponentModel;
+using System.ComponentModel.DataAnnotations;
 
 namespace LeafWeb.WebCms.Models
 {
@@ -57,10 +58,17 @@ namespace LeafWeb.WebCms.Models
         public string phips2 { get; set; }
 
         [Display(Name = "Show Only Successfully Completed")]
-        public bool? compl { get; set; }
+        [UIHint("Checkbox")]
+        public string compl { get; set; }
+
+        public bool ShowOnlySuccessfullyCompleted => !string.IsNullOrEmpty(compl);
 
         [Display(Name = "Only my data")]
-        public bool? usr { get; set; }
+        [UIHint("Checkbox")]
+        public string usr { get; set; }
+
+        public bool OnlyUserData => !string.IsNullOrEmpty(usr);
+
 
         public bool HasExtendedParameters =>
             !(
@@ -74,12 +82,12 @@ namespace LeafWeb.WebCms.Models
                 && string.IsNullOrEmpty(pari)
                 && string.IsNullOrEmpty(tleaf)
                 && string.IsNullOrEmpty(phips2)
-                && !(compl.HasValue && compl.Value)
+                && string.IsNullOrEmpty(compl)
             );
 
         public bool HasParameters =>
             HasExtendedParameters 
             || !string.IsNullOrEmpty(q) 
-            || usr.HasValue && usr.Value;
+            || !string.IsNullOrEmpty(usr);
     }
 }