Add concurrency checks.

See also:
https://learn.microsoft.com/en-us/ef/core/saving/concurrency?tabs=data-annotations

EntityFrameworkCore.Console/Program.cs

@@ -22,6 +22,23 @@ context.Database.EnsureCreated();
 // Rather than raise: "System.InvalidOperationException: Sequence contains no elements."
 // var firstCoach = await context.Coaches.FirstOrDefaultAsync();
 
+async Task ConcurrencyCheckExample()
+{
+  var team = context.Teams.Find(1);
+  team.Name = "New name";
+
+  // To simulate a concurrency change, add a breakpoint and
+  // manually update the GUID in the database before SaveChangesAsync is called.
+  // See also: https://learn.microsoft.com/en-us/ef/core/saving/concurrency?tabs=data-annotations
+  try
+  {
+    await context.SaveChangesAsync();
+  }
+  catch (DbUpdateConcurrencyException ex)
+  {
+    Console.WriteLine(ex.Message);
+  }
+}
 
 async Task TransactionWithSavepoint()
 {

EntityFrameworkCore.Data/Configurations/TeamConfiguration.cs

@@ -13,6 +13,12 @@ public class TeamConfiguration : IEntityTypeConfiguration<Team>
     // example composite key configuration.
     // builder.HasIndex(λ => new { λ.CoachId, λ.LeagueId }).IsUnique();
 
+    // SQL Server method to setup concurrency.
+    // builder.Property(λ => λ.Version).IsRowVersion();
+
+    // SQLite (and other) method to setup concurrency. See also BaseDomain model.
+    builder.Property(λ => λ.Version).IsConcurrencyToken();
+
     builder.Property(λ => λ.Name).HasMaxLength(100).IsRequired();
 
     builder.HasMany(m => m.HomeMatches) // A team has many home matches.

EntityFrameworkCore.Data/DeadBallZoneLeagueDbContext.cs

@@ -65,6 +65,9 @@ public class DeadBallZoneLeagueDbContext : DbContext
         entry.Entity.CreatedDate = DateTime.UtcNow;
         entry.Entity.CreatedBy = "Sample User";
       }
+
+      // Update the concurrency token.
+      entry.Entity.Version = Guid.NewGuid();
     }
     return base.SaveChangesAsync(cancellationToken);
   }

EntityFrameworkCore.Domain/BaseDomainModel.cs

@@ -1,4 +1,6 @@
-namespace EntityFrameworkCore.Domain;
+using System.ComponentModel.DataAnnotations;
+
+namespace EntityFrameworkCore.Domain;
 // Since C#11, you do not need to wrap in accolades anymore.
 public abstract class BaseDomainModel
 {
@@ -7,4 +9,12 @@ public abstract class BaseDomainModel
   public DateTime ModifiedDate { get; set;}
   public string? CreatedBy { get; set; }
   public string? ModifiedBy { get; set; }
+
+  // SQL Server method to setup concurrency column.
+  // [Timestamp]
+  // public byte[] Version { get; set; }
+
+  // SQLite (and other) method to setup concurrency column.
+  [ConcurrencyCheck]
+  public Guid Version { get; set; }
 }