无法使用 Dapper 创建数据库并且数据库名称作为 @ 变量传入，为什么？

Question

我有一个用 dapper 创建数据库的代码：

public static bool CreateDatabase(string connectionString, string databaseName)
{
    const string DATABASE_CREATE_QUERY = "CREATE DATABASE (@databaseName)";

    using (var connection = new SqlConnection(connectionString))
    {
        var affectedRows = connection.Execute(DATABASE_CREATE_QUERY, new { databaseName });

        return affectedRows > 0 ? true : false;
    }
}

CreateDatabase("Server=10.10.10.10;User ID=user;Password=password;MultipleActiveResultSets=true;", "TEST_DB");

每次运行此方法时，都会出现错误：

“(”附近的语法不正确。

有踪迹：

at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
at System.Data.SqlClient.SqlInternalConnection.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.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString, Boolean isInternal, Boolean forDescribeParameterEncryption, Boolean shouldCacheForAlwaysEncrypted)
at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, Boolean inRetry, SqlDataReader ds, Boolean describeParameterEncryptionRequest)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry)
at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry)
at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
at Dapper.SqlMapper.ExecuteCommand(IDbConnection cnn, CommandDefinition& command, Action`2 paramReader) in E:\GitHub\Dapper\Dapper\SqlMapper.cs:line 2827
at Dapper.SqlMapper.ExecuteImpl(IDbConnection cnn, CommandDefinition& command) in E:\GitHub\Dapper\Dapper\SqlMapper.cs:line 570
at Dapper.SqlMapper.Execute(IDbConnection cnn, String sql, Object param, IDbTransaction transaction, Nullable`1 commandTimeout, Nullable`1 commandType) in E:\GitHub\Dapper\Dapper\SqlMapper.cs:line 443
at DbCreator.DbUtils.CreateDatabase(String connectionString, String databaseName) in E:\src_projects\DbCreator\DbUtils.cs:line 48
at DbCreator.***.Run(String connectionString) in E:\src_projects\DbCreator\***.cs:line 23

如果我以丑陋的方式设置查询

const string DATABASE_CREATE_QUERY = $"CREATE DATABASE {databaseName}";

并运行

connection.Execute(DATABASE_CREATE_QUERY);

一切正常。

如果我在 QUERY 中不使用方括号 ()

const string DATABASE_CREATE_QUERY = "CREATE DATABASE @databaseName";

我收到错误：

“@databaseName”附近的语法不正确

我也尝试过 ExecuteScalar、Query 方法，但结果相同。

有什么想法为什么这不能以 Dapper 的方式工作吗？

Answer 1

这是因为 sp_executesql 被用于参数化。这是通过 Dapper 解释在数据库中执行的内容；

exec sp_executesql N'Create Database (@DBName)',N'@DBName nvarchar(4000)',@DBName=N'Test'

了解为什么这不适用于 sp_executesql：表名作为变量

最好的选择是创建一个存储过程，或者使用字符串替换的方法。