From 03e1e0e9bc785fafb883b3a2729eb68d741531a5 Mon Sep 17 00:00:00 2001
From: Sebastian Mayer <sebastian.mayer@trumpf.com>
Date: Mon, 30 Sep 2019 15:50:40 +0200
Subject: [PATCH] provide possibility to override expression used for
 validation

---
 .../Components/Base/BaseMatInputComponent.cs   | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/MatBlazor/Components/Base/BaseMatInputComponent.cs b/src/MatBlazor/Components/Base/BaseMatInputComponent.cs
index e975da30..6f9c27a5 100644
--- a/src/MatBlazor/Components/Base/BaseMatInputComponent.cs
+++ b/src/MatBlazor/Components/Base/BaseMatInputComponent.cs
@@ -1,4 +1,4 @@
-using Microsoft.AspNetCore.Components;
+using Microsoft.AspNetCore.Components;
 using Microsoft.AspNetCore.Components.Forms;
 using System;
 using System.Collections.Generic;
@@ -80,7 +80,13 @@ protected void NotifyFieldChanged()
         /// Gets or sets an expression that identifies the bound value.
         /// </summary>
         [Parameter]
-        public Expression<Func<T>> ValueExpression { get; set; }
+        public Expression<Func<T>> ValueExpression { get; set; }
+
+        /// <summary>
+        /// Gets or sets an expression that identifies the bound value to validate.
+        /// </summary>
+        [Parameter]
+        public Expression<Func<T>> ValidateValueExpression { get; set; }
 
         /// <inheritdoc />
         public override Task SetParametersAsync(ParameterView parameters)
@@ -97,13 +103,13 @@ public override Task SetParametersAsync(ParameterView parameters)
                     EditContext = CascadedEditContext;
                     if (EditContext != null)
                     {
-                        if (ValueExpression == null)
+                        if (ValueExpression == null && ValidateValueExpression == null)
                         {
-                            throw new InvalidOperationException($"{GetType()} requires a value for the 'ValueExpression' " +
+                            throw new InvalidOperationException($"{GetType()} requires a value for the 'ValueExpression'" +
                                                                 $"parameter. Normally this is provided automatically when using 'bind-Value'.");
                         }
 
-                        FieldIdentifier = FieldIdentifier.Create(ValueExpression);
+                        FieldIdentifier = FieldIdentifier.Create(ValidateValueExpression ?? ValueExpression);
                     }
 
                     _hasSetInitialEditContext = true;
@@ -124,4 +130,4 @@ public override Task SetParametersAsync(ParameterView parameters)
             return base.SetParametersAsync(ParameterView.Empty);
         }
     }
-}
\ No newline at end of file
+}