[#43] AreaComAdminWindow: Do not use Context from ContextWindow any more

Elwig/Helpers/Validator.cs

@@ -576,7 +576,7 @@ namespace Elwig.Helpers {
             }
         }
 
-        public static ValidationResult CheckFbNr(TextBox input, bool required, AppDbContext ctx, AreaCom? c) {
+        public static ValidationResult CheckFbNr(TextBox input, bool required, AreaCom? c) {
             var res = CheckInteger(input, required);
             if (!res.IsValid) {
                 return res;
@@ -584,6 +584,7 @@ namespace Elwig.Helpers {
                 return new(true, null);
             }
 
+            using var ctx = new AppDbContext();
             int nr = int.Parse(input.Text);
             if (nr != c?.FbNr && ctx.FbNrExists(nr).GetAwaiter().GetResult()) {
                 return new(false, "Flächenbindungsnummer wird bereits verwendet");