Add EditContext.IsValid(..) to determine if a field has any associated validation messages (#48698)

* Add EditContext.IsValid(..) to determine if a field has any associated validation messages

* refactor and add tests

* fix judge

Author: ElderJames

src/Components/Forms/src/EditContext.cs

@@ -195,6 +195,21 @@ public bool IsModified(in FieldIdentifier fieldIdentifier)
     public bool IsModified(Expression<Func<object>> accessor)
         => IsModified(FieldIdentifier.Create(accessor));
 
+    /// <summary>
+    /// Determines whether the specified fields in this <see cref="EditContext"/> has no associated validation messages.
+    /// </summary>
+    /// <returns>True if the field has no associated validation messages after validation; otherwise false.</returns>
+    public bool IsValid(in FieldIdentifier fieldIdentifier)
+        => !GetValidationMessages(fieldIdentifier).Any();
+
+    /// <summary>
+    /// Determines whether the specified fields in this <see cref="EditContext"/> has no associated validation messages.
+    /// </summary>
+    /// <param name="accessor">Identifies the field whose current validation messages should be returned.</param>
+    /// <returns>True if the field has no associated validation messages after validation; otherwise false.</returns>
+    public bool IsValid(Expression<Func<object>> accessor)
+        => IsValid(FieldIdentifier.Create(accessor));
+
     /// <summary>
     /// Validates this <see cref="EditContext"/>.
     /// </summary>

src/Components/Forms/src/PublicAPI.Unshipped.txt

@@ -1,3 +1,5 @@
 #nullable enable
 Microsoft.AspNetCore.Components.Forms.EditContext.ShouldUseFieldIdentifiers.get -> bool
 Microsoft.AspNetCore.Components.Forms.EditContext.ShouldUseFieldIdentifiers.set -> void
+Microsoft.AspNetCore.Components.Forms.EditContext.IsValid(in Microsoft.AspNetCore.Components.Forms.FieldIdentifier fieldIdentifier) -> bool
+Microsoft.AspNetCore.Components.Forms.EditContext.IsValid(System.Linq.Expressions.Expression<System.Func<object!>!>! accessor) -> bool

src/Components/Forms/test/EditContextTest.cs

@@ -233,6 +233,24 @@ public void RequestsValidationWhenValidateIsCalled()
         Assert.Equal(new[] { "Some message" }, editContext.GetValidationMessages());
     }
 
+    [Fact]
+    public void IsInvalidWithValidationMessagesForSpecifiedField()
+    {
+        // Arrange
+        var editContext = new EditContext(new object());
+        var messages = new ValidationMessageStore(editContext);
+        var fieldOnThisModel1 = editContext.Field("field1");
+        var fieldOnThisModel2 = editContext.Field("field2");
+        messages.Add(
+            fieldOnThisModel1,
+            "Some message");
+
+        // Assert
+        Assert.False(editContext.Validate());
+        Assert.False(editContext.IsValid(fieldOnThisModel1));
+        Assert.True(editContext.IsValid(fieldOnThisModel2));
+    }
+
     [Fact]
     public void LookingUpModel_ThatOverridesGetHashCodeAndEquals_Works()
     {