添加项目文件。

FileService.Domain/ValueObjects/FileName.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace FileService.Domain.ValueObjects
+{
+    public class FileName
+    {
+        public string Value { get; }
+
+        public FileName(string value)
+        {
+            if(value.Length > 20)
+            {
+                throw new ArgumentException("文件名超出长度");
+            }
+
+            Value = value;
+        }
+
+        public override string ToString()
+        {
+            return Value;
+        }
+
+        public static implicit operator FileName(string value)
+        {
+            return new FileName(value);
+        }
+
+    }
+}