Galen.Ci.EntityFramework.DbDeploymentManager.GetPendingMigration C# (CSharp) Method

        private MigrationExecutionInfo GetPendingMigration()
        {
            ValidateConfiguredAssemblies();

            var hasDeployedAssembly = (this.DeployedAssembly != null);
            var deployedMigrationInfo = hasDeployedAssembly
                ? GetMigrationInfo(MigrationsSource.Deployed)
                : null;

            var targetMigrationInfo = GetMigrationInfo(MigrationsSource.Target);

            if (targetMigrationInfo.Source == MigrationsSource.Target
                && targetMigrationInfo.GenericMigrator == null
                && hasDeployedAssembly)
            {
                //The target assembly does not contain a matching migrator / migration config
                //This means we are rolling back past to a time before this context existed
                //So we should use the deployed assembly migration with a target of "0"

                var isDeployedAssemblyHasConfiguration = 
                    deployedMigrationInfo.GenericMigrator.Configuration.GetType().FullName ==
                    targetMigrationInfo.ConfigurationType;

                if (!isDeployedAssemblyHasConfiguration)
                {
                    throw new InvalidOperationException("Deployed migration missing required migration configuration");
                }

                return new MigrationExecutionInfo
                {
                    Migration = deployedMigrationInfo,
                    TargetMigrationId = "0" //Before initial create
                };
            }
            else
            {
                var isDeployedAssemblyHasConfiguration = (deployedMigrationInfo != null) &&
                    (deployedMigrationInfo.GenericMigrator.Configuration.GetType().FullName ==
                     targetMigrationInfo.GenericMigrator.Configuration.GetType().FullName)
                    &&
                    (deployedMigrationInfo.GenericMigrator.Configuration.ContextType.FullName ==
                     targetMigrationInfo.GenericMigrator.Configuration.ContextType.FullName);

                if (!isDeployedAssemblyHasConfiguration)
                {
                    // there is no matching deployed migration, so just use the target
                    return new MigrationExecutionInfo {Migration = targetMigrationInfo};
                }

                if (targetMigrationInfo.GenericMigrator != null)
                {
                    string targetMigrationId = targetMigrationInfo.GenericMigrator
                        .GetLocalMigrations()
                        .OrderBy(i => i)
                        .LastOrDefault();

                    if (string.IsNullOrEmpty(targetMigrationId))
                    {
                        return null;
                    }

                    string lastDeployedMigrationId = deployedMigrationInfo.GenericMigrator
                        .GetLocalMigrations()
                        .OrderBy(i => i)
                        .LastOrDefault();

                    Log.Debug(
                        "Last migration deployed is {lastDeployedMigrationId}.  Latest target migration is {targetMigrationId}.",
                        lastDeployedMigrationId,
                        targetMigrationId);

                    var migrationComparisonResult = targetMigrationId.CompareTo(lastDeployedMigrationId);
                    if (migrationComparisonResult == 0)
                    {
                        // target migration is equal to the latest deployed migration
                        // so there is no migration to execute
                        return null;
                    }

                    var isUpwardMigration = (migrationComparisonResult > 0);
                    return new MigrationExecutionInfo
                    {
                        TargetMigrationId = targetMigrationId,
                        Migration = isUpwardMigration
                            ? targetMigrationInfo
                            : deployedMigrationInfo
                    };
                }

                return null;
            }
        }