hc:DatePicker support for Validation

src/Shared/HandyControl_Shared/Controls/Input/CheckComboBox/CheckComboBox.cs

@@ -188,7 +188,7 @@ namespace HandyControl.Controls
             var isError = !result.Data;
             if (isError)
             {
-                SetCurrentValue(IsErrorProperty, true);
+                SetCurrentValue(IsErrorProperty, ValueBoxes.TrueBox);
                 SetCurrentValue(ErrorStrProperty, result.Message);
             }
             else

src/Shared/HandyControl_Shared/Controls/Input/ComboBox.cs

@@ -360,7 +360,7 @@ namespace HandyControl.Controls
             var isError = !result.Data;
             if (isError)
             {
-                SetCurrentValue(IsErrorProperty, true);
+                SetCurrentValue(IsErrorProperty, ValueBoxes.TrueBox);
                 SetCurrentValue(ErrorStrProperty, result.Message);
             }
             else

src/Shared/HandyControl_Shared/Controls/Input/DatePicker.cs

@@ -153,9 +153,21 @@ namespace HandyControl.Controls
                 }
             }
 
-            IsError = !result.Data;
-            ErrorStr = result.Message;
-            return result.Data;
+            var isError = !result.Data;
+            if (isError)
+            {
+                SetCurrentValue(IsErrorProperty, true);
+                SetCurrentValue(ErrorStrProperty, result.Message);
+            }
+            else
+            {
+                isError = Validation.GetHasError(this);
+                if (isError)
+                {
+                    SetCurrentValue(ErrorStrProperty, Validation.GetErrors(this)[0].ErrorContent);
+                }
+            }
+            return !isError;
         }
     }
 }

src/Shared/HandyControl_Shared/Controls/Input/NumericUpDown.cs

@@ -120,7 +120,7 @@ namespace HandyControl.Controls
                 Value = 0;
 
                 SetCurrentValue(ErrorStrProperty, string.Empty);
-                SetCurrentValue(IsErrorProperty, false);
+                SetCurrentValue(IsErrorProperty, ValueBoxes.FalseBox);
             }
             else if (double.TryParse(_textBox.Text, out var value))
             {
@@ -129,7 +129,7 @@ namespace HandyControl.Controls
                 if (Validation.GetHasError(this))
                 {
                     SetCurrentValue(ErrorStrProperty, Validation.GetErrors(this)[0].ErrorContent);
-                    SetCurrentValue(IsErrorProperty, true);
+                    SetCurrentValue(IsErrorProperty, ValueBoxes.TrueBox);
                 }
             }
 
@@ -513,7 +513,7 @@ namespace HandyControl.Controls
             }
 
             SetCurrentValue(ErrorStrProperty, result.Message);
-            SetCurrentValue(IsErrorProperty, !result.Data);
+            SetCurrentValue(IsErrorProperty, ValueBoxes.BooleanBox(!result.Data));
             return result.Data;
         }
     }

src/Shared/HandyControl_Shared/Controls/Input/TextBox.cs

@@ -115,7 +115,7 @@ namespace HandyControl.Controls
             var isError = !result.Data;
             if (isError)
             {
-                SetCurrentValue(IsErrorProperty, true);
+                SetCurrentValue(IsErrorProperty, ValueBoxes.TrueBox);
                 SetCurrentValue(ErrorStrProperty, result.Message);
             }
             else