Add extension method for FieldProvider Property invoke to avoid explicit cast (#5700)

Author: live1206

packages/http-client-csharp/generator/Microsoft.Generator.CSharp/src/Snippets/Snippet.cs

@@ -120,6 +120,9 @@ public static InvokeMethodExpression Invoke(this ParameterProvider parameter, st
         public static ValueExpression Property(this ParameterProvider parameter, string propertyName, bool nullConditional = false)
             => new MemberExpression(nullConditional ? new NullConditionalExpression(parameter) : parameter, propertyName);
 
+        public static ValueExpression Property(this FieldProvider field, string propertyName, bool nullConditional = false)
+            => new MemberExpression(nullConditional ? new NullConditionalExpression(field) : field, propertyName);
+
         public static InvokeMethodExpression Invoke(this FieldProvider field, string methodName, IEnumerable<ValueExpression> parameters)
             => field.Invoke(methodName, parameters, false, false);