Converted Tag to ValueObject

Author: linkdotnet

LinkDotNet.Blog.Domain/BlogPost.cs

@@ -43,7 +43,7 @@ public static BlogPost Create(
             UpdatedDate = updatedDate ?? DateTime.Now,
             PreviewImageUrl = previewImageUrl,
             IsPublished = isPublished,
-            Tags = tags?.Select(t => new Tag { Content = t.Trim() }).ToList(),
+            Tags = tags?.Select(Tag.Create).ToList(),
         };
 
         return blogPost;

LinkDotNet.Blog.Domain/Tag.cs

@@ -1,8 +1,27 @@
-namespace LinkDotNet.Blog.Domain;
+using System;
+
+namespace LinkDotNet.Blog.Domain;
 
 public class Tag
 {
-    public string Id { get; set; }
+    private Tag()
+    {
+    }
+
+    public string Id { get; private set; }
+
+    public string Content { get; private set; }
+
+    public static Tag Create(string content)
+    {
+        if (string.IsNullOrWhiteSpace(content))
+        {
+            throw new ArgumentNullException(nameof(content));
+        }
 
-    public string Content { get; set; }
+        return new Tag
+        {
+            Content = content.Trim(),
+        };
+    }
 }

LinkDotNet.Blog.UnitTests/Domain/TagTests.cs

@@ -0,0 +1,28 @@
+using System;
+using FluentAssertions;
+using LinkDotNet.Blog.Domain;
+using Xunit;
+
+namespace LinkDotNet.Blog.UnitTests.Domain;
+
+public class TagTests
+{
+    [Fact]
+    public void ShouldCreateTag()
+    {
+        var tag = Tag.Create(" Test ");
+
+        tag.Content.Should().Be("Test");
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData(null)]
+    [InlineData(" ")]
+    public void ShouldThrowExceptionIfInvalid(string content)
+    {
+        Action act = () => Tag.Create(content);
+
+        act.Should().Throw<ArgumentNullException>();
+    }
+}