rewrite number whatever to .net and blazor.

Data/AppDbContext.cs

@@ -0,0 +1,21 @@
+using Microsoft.EntityFrameworkCore;
+using landing.Models;
+
+namespace landing.Data;
+
+public class AppDbContext : DbContext
+{
+    public AppDbContext(DbContextOptions<AppDbContext> options) : base(options) { }
+
+    public DbSet<Subscriber> Subscribers => Set<Subscriber>();
+    public DbSet<Newsletter> Newsletters => Set<Newsletter>();
+    public DbSet<ContactMessage> ContactMessages => Set<ContactMessage>();
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        modelBuilder.Entity<Subscriber>(entity =>
+        {
+            entity.HasIndex(e => e.Email).IsUnique();
+        });
+    }
+}