feat(Table): support navigation property null value (#7296)

* fix: 修复复杂导航属性获取值表达式不支持 null 值问题

* chore: bump version 10.1.4-beta01

* refactor: 优化代码

Author: ArgoZhang

src/BootstrapBlazor/BootstrapBlazor.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Razor">
 
   <PropertyGroup>
-    <Version>10.1.3</Version>
+    <Version>10.1.4-beta01</Version>
   </PropertyGroup>
 
   <ItemGroup>

src/BootstrapBlazor/Extensions/LambdaExtensions.cs

@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the Apache 2.0 License
 // See the LICENSE file in the project root for more information.
 // Maintainer: Argo Zhang(argo@live.ca) Website: https://www.blazor.zone
@@ -662,24 +662,27 @@ Expression<Func<TModel, TResult>> GetSimplePropertyExpression()
         Expression<Func<TModel, TResult>> GetComplexPropertyExpression()
         {
             var propertyNames = propertyName.Split(".");
-            Expression? body = null;
-            Type t = type;
-            object? propertyInstance = model;
+            Expression body = Expression.Convert(parameter, type);
             foreach (var name in propertyNames)
             {
-                var p = t.GetPropertyByName(name) ?? throw new InvalidOperationException($"类型 {type.Name} 未找到 {name} 属性，无法获取其值");
-                propertyInstance = p.GetValue(propertyInstance);
-                if (propertyInstance != null)
-                {
-                    t = propertyInstance.GetType();
-                }
-
-                body = Expression.Property(body ?? Expression.Convert(parameter, type), p);
+                body = BuildPropertyAccess(body, body.Type, name);
             }
-            return Expression.Lambda<Func<TModel, TResult>>(Expression.Convert(body!, typeof(TResult)), parameter);
+            return Expression.Lambda<Func<TModel, TResult>>(Expression.Convert(body, typeof(TResult)), parameter);
         }
     }
 
+    private static ConditionalExpression BuildPropertyAccess(Expression instance, Type instanceType, string propertyName)
+    {
+        var p = instanceType.GetPropertyByName(propertyName) ?? throw new InvalidOperationException($"类型 {instanceType.Name} 未找到 {propertyName} 属性，无法获取其值");
+
+        var propertyAccess = Expression.Property(instance, p);
+        return Expression.Condition(
+            test: Expression.Equal(instance, Expression.Constant(null, instanceType)),
+            ifTrue: Expression.Constant(null, p.PropertyType),
+            ifFalse: propertyAccess
+        );
+    }
+
     /// <summary>
     /// 给指定模型属性赋值 Lambda 表达式
     /// </summary>