添加项目文件。

Sai.Toolkit.Mvvm/Attributes/NotNullOrEmptyAttribute.cs

@@ -0,0 +1,13 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace Sai.Toolkit.Mvvm.Attributes;
+
+[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter)]
+public sealed class NotNullOrEmptyAttribute : ValidationAttribute
+{
+    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
+    {
+        var b = value != null || (value is string str && !string.IsNullOrEmpty(str));
+        return b ? ValidationResult.Success : new("输入内容不是数值。");
+    }
+}