Update-Database command is not working in ASP.Net Core / Entity Framework Core because object in database already exists

问题

I was updating my database by the command line, but then I manually updated one of my tables.

This seems to have disrupted my ability to update-database. I receive the following error when I try to update:

 System.Data.SqlClient.SqlException: There is already an object named 'ClientsAndTestimonials' in the database.    at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
    at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout, Boolean asyncWrite)
    at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite, String methodName)
    at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
    at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.Execute(IRelationalConnection connection, String executeMethod, IReadOnlyDictionary`2 parameterValues, Boolean openConnection, Boolean closeConnection) 
    at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.ExecuteNonQuery(IRelationalConnection connection, IReadOnlyDictionary`2 parameterValues, Boolean manageConnection) 
    at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationCommandExecutor.ExecuteNonQuery(IEnumerable`1 migrationCommands, IRelationalConnection connection) 
    at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration) 
    at Microsoft.EntityFrameworkCore.Design.MigrationsOperations.UpdateDatabase(String targetMigration, String contextType) 
    at Microsoft.EntityFrameworkCore.Tools.Cli.DatabaseUpdateCommand.<>c__DisplayClass0_0.<Configure>b__0() 
    at Microsoft.Extensions.CommandLineUtils.CommandLineApplication.Execute(String[] args)
    at Microsoft.EntityFrameworkCore.Tools.Cli.Program.Main(String[] args)
 ClientConnectionId:d89989a8-ce8b-4167-be7e-fcddc4bcdf98
 Error Number:2714,State:6,Class:16
 There is already an object named 'ClientsAndTestimonials' in the database. 

I have been trying to fix this problem for the past few days. Most fellow developers suggest some variation of using Add-migration "Reset" -IgnoreChanges, like John Salewski from the following link.

However, I keep getting an error that says "A parameter cannot be found that matches parameter name 'IgnoreChanges'".

Any suggestions would be greatly appreciated!

回答1:

First, that is not EF 6, it is EF Core. There is no -IgnoreChanges currently in EF Core (see here) but you can achieve the equivalent by commenting out all the code in the Up() method and applying the migration. This will take a snapshot of the current model state so that subsequent migrations will only include changes from that point forward.

So if you just made some incremental model change and you don't have this initial baseline you may need to remove those changes, apply the baseline migration, then add your changes back and add a 2nd migration.

回答2:

Use Alter column instead AddColumn in up() function

    migrationBuilder.AlterColumn<bool>(
        name: "IsActive",
        table: "Advertisements",
        nullable: false,
        defaultValue: true);

You can remark some parts in up function if you dont want to full effect to database.

If your migration command angried for making those. Reset and rebase migration. How: Delete migration content both from visualstudio and sql and add-migration again and update-database

来源：https://stackoverflow.com/questions/43687433/update-database-command-is-not-working-in-asp-net-core-entity-framework-core-b