添加项目文件。

WaterCloud.Code/Provider/ModelBindingMetadataProvider.cs

@@ -0,0 +1,18 @@
+using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
+
+namespace WaterCloud.Code
+{
+	/// <summary>
+	/// Controller Model Binding 处理
+	/// </summary>
+	public class ModelBindingMetadataProvider : IMetadataDetailsProvider, IDisplayMetadataProvider
+	{
+		public void CreateDisplayMetadata(DisplayMetadataProviderContext context)
+		{
+			if (context.Key.MetadataKind == ModelMetadataKind.Property)
+			{
+				context.DisplayMetadata.ConvertEmptyStringToNull = false;
+			}
+		}
+	}
+}