Styjun

I'm setting up Entity Framework Core in a new API to deploy to an existing SQL Server database that is used by Entity Framework 4.6 applications. There is one Migration History table that is shared by other applications, and has 2 fields in it that need to be populated for each entry: ContextKey, and Model. Entity Framework Core does not have a Context Key, and does not save the Model to the Migration History table.

I've already created a HistoryRepository : SqlServerHistoryRepository and configured Entity Framework Core to use it, but the ConfigureTable method only allows you to create additional columns, but not actually populate each record as it gets inserted with custom data. Providing a default value to the column is not a solution.

public class HistoryRepository : SqlServerHistoryRepository

 public HistoryRepository(HistoryRepositoryDependencies dependencies)
 : base(dependencies)
 
 
 protected override void ConfigureTable(EntityTypeBuilder<HistoryRow> history)
 
 base.ConfigureTable(history);
 history.Property<string>("ContextKey")
 .HasMaxLength(300);
 history.Property<byte[]>("Model");
 


 services.AddDbContext<MDSContext>(options =>
 options.UseLazyLoadingProxies()
 .UseSqlServer(
 connectionString,
 x => x.MigrationsHistoryTable("__MigrationHistory")).ReplaceService<Microsoft.EntityFrameworkCore.Migrations.IHistoryRepository, Burkhart.CoreServices.IncomingOrders.Core.Models.Base.HistoryRepository>()
 );

I should be able to provide a custom value for ContextKey and Model dynamically

I looked all over for solutions, but they all show you how to add a column and set a default value, but not how to set a value dynamically. I ended up digging into the ASP.NET Entity Framework Core source code at GitHub for the solution, so that I would share it with everyone else, as I know there are others that are looking for this information:

Just override the GetInsertScript method on the HistoryRepository and insert your custom values. Here is the full solution:

public class HistoryRepository : SqlServerHistoryRepository

 public HistoryRepository(HistoryRepositoryDependencies dependencies)
 : base(dependencies)
 
 
 protected override void ConfigureTable(EntityTypeBuilder<HistoryRow> history)
 
 base.ConfigureTable(history);
 history.Property<string>("ContextKey")
 .HasMaxLength(300);
 history.Property<byte[]>("Model");
 
 public override string GetInsertScript(HistoryRow row)
 
 var stringTypeMapping = Dependencies.TypeMappingSource.GetMapping(typeof(string));
 return new StringBuilder().Append("INSERT INTO ")
 .Append(SqlGenerationHelper.DelimitIdentifier(TableName, TableSchema))
 .Append(" (")
 .Append(SqlGenerationHelper.DelimitIdentifier(MigrationIdColumnName))
 .Append(", ")
 .Append(SqlGenerationHelper.DelimitIdentifier(ProductVersionColumnName))
 .Append(", [ContextKey], [Model])")
 .Append("VALUES (")
 .Append(stringTypeMapping.GenerateSqlLiteral(row.MigrationId))
 .Append(", ")
 .Append(stringTypeMapping.GenerateSqlLiteral(row.ProductVersion))
 .Append($", 'ContextConstants.ContextName.ContextConstants.ContextSchemaName', 0x)")
 .AppendLine(SqlGenerationHelper.StatementTerminator)
 .ToString();
 

Here is a link to the source code on github:
https://github.com/aspnet/EntityFrameworkCore/blob/master/src/EFCore.Relational/Migrations/HistoryRepository.cs