无法将参数值从 List`1 转换为 IEnumerable`1

Question

我正在将表值参数传递给 StoredProcedure。

请在下面检查我的代码

CREATE TYPE TempTable AS TABLE 
(A nvarchar(50), B nvarchar(50), C nvarchar(500))


 SqlParameter[] param = new SqlParameter[3];
 param[0] = new SqlParameter("@A", A);
 param[1] = new SqlParameter("@B", B);
 param[2] = new SqlParameter("@C", lstC);
 param[2].SqlDbType = SqlDbType.Structured;
 param[2].TypeName = "dbo.TempTable ";

 DataSet ds = SqlHelper.ExecuteDataset("StoredProcedureName", param);

这里，lstC是类的 List 对象。

但得到错误“ Failed to convert parameter value from a List1 to a IEnumerable1.”

编辑

 public static DataSet ExecuteDataset(string spName, params object[] parameterValues)
    {
        if (connectionString == null || connectionString.Length == 0) throw new ArgumentNullException("connectionString");
        if (spName == null || spName.Length == 0) throw new ArgumentNullException("spName");

        // If we receive parameter values, we need to figure out where they go
        if ((parameterValues != null) && (parameterValues.Length > 0))
        {
            // Pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
            SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);

            // Assign the provided values to these parameters based on parameter order
            AssignParameterValues(commandParameters, parameterValues);

            // Call the overload that takes an array of SqlParameters
            return ExecuteDataset(CommandType.StoredProcedure, spName, commandParameters);
        }
        else
        {
            // Otherwise we can just call the SP without params
            return ExecuteDataset(CommandType.StoredProcedure, spName);
        }
  }



 public static DataSet ExecuteDataset(CommandType commandType, string commandText, params SqlParameter[] commandParameters)
    {
        if (connectionString == null || connectionString.Length == 0) throw new ArgumentNullException("connectionString");

        // Create & open a SqlConnection, and dispose of it after we are done
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();

            // Call the overload that takes a connection in place of the connection string
            return ExecuteDataset(connection, commandType, commandText, commandParameters);
        }
    }

   public static DataSet ExecuteDataset(SqlConnection connection, CommandType commandType,   String commandText, params SqlParameter[] commandParameters)
    {
        if (connection == null) throw new ArgumentNullException("connection");

        // Create a command and prepare it for execution
        SqlCommand cmd = new SqlCommand();
        bool mustCloseConnection = false;
        PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters, out mustCloseConnection);

        // Create the DataAdapter & DataSet
        using (SqlDataAdapter da = new SqlDataAdapter(cmd))
        {
            DataSet ds = new DataSet();
            cmd.CommandTimeout = 0;
            // Fill the DataSet using default values for DataTable names, etc
            da.Fill(ds);

            // Detach the SqlParameters from the command object, so they can be used again
            cmd.Parameters.Clear();

            if (mustCloseConnection)
                connection.Close();

            // Return the dataset
            return ds;
        }
    }

准备命令

private static void PrepareCommand(SqlCommand command, SqlConnection connection, SqlTransaction transaction, CommandType commandType, string commandText, SqlParameter[] commandParameters, out bool mustCloseConnection)
    {
        if (command == null) throw new ArgumentNullException("command");
        if (commandText == null || commandText.Length == 0) throw new ArgumentNullException("commandText");

        // If the provided connection is not open, we will open it
        if (connection.State != ConnectionState.Open)
        {
            mustCloseConnection = true;
            connection.Open();
        }
        else
        {
            mustCloseConnection = false;
        }

        // Associate the connection with the command
        command.Connection = connection;

        // Set the command text (stored procedure name or SQL statement)
        command.CommandText = commandText;

        // If we were provided a transaction, assign it
        if (transaction != null)
        {
            if (transaction.Connection == null) throw new ArgumentException("The transaction was rollbacked or commited, please provide an open transaction.", "transaction");
            command.Transaction = transaction;
        }

        // Set the command type
        command.CommandType = commandType;

        // Attach the command parameters if they are provided
        if (commandParameters != null)
        {
            AttachParameters(command, commandParameters);
        }
        return;
    }

Answer 1

在项目更新到 .Net Core 3.1 期间来到这里，并开始在以前工作的代码上收到此错误。如果您要使用 Core 3.1+，这可能仅对您有所帮助

原来这是我在创建结构化数据以发送到我的 sproc 时使用的 SqlDataRecord类型的问题。

旧的：Microsoft.SqlServer.Server.SqlDataRecord
新的：Microsoft.Data.SqlClient.Server.SqlDataRecord

请注意，根据他们对 .Net Core 3.1 及更高版本的建议，我还从 System.Data.SqlClient 转移到了 Microsoft.Data.SqlClient，并在找到开始这篇文章的错误之前清除了另一个错误。

Answer 2

如果您通过参数传递表数据，则需要使用用户定义的表类型，例如：

CREATE TYPE [dbo].[TempTable] AS TABLE(
    [A] [varchar](50) NULL,
    [B] [varchar](50) NULL,
    [C] [varchar](500) NULL,
)

并且lstC应该是一个DataTableorIEnumerable<SqlDataRecord>而不仅仅是您自己的类的列表。

尝试：

param[2] = new SqlParameter("@C", lstC.Select(c => c.ToSqlDataRecord()));

ToSqlDataRecord你的类中的辅助函数在哪里？例子：

public class Thing {

    public string A { get; set; }

    public string B { get; set; }

    public string C { get; set; }

    // to match the dbo.TempTable User-Defined Table Type on database
    private static readonly SqlMetaData[] myRecordSchema = {
        new SqlMetaData("A", SqlDbType.VarChar, 50),
        new SqlMetaData("B", SqlDbType.VarChar, 50),
        new SqlMetaData("C", SqlDbType.VarChar, 500)
    };

    public SqlDataRecord ToSqlDataRecord() {
        var record = new SqlDataRecord(myRecordSchema);
        record.SetString(0, A);
        record.SetDateTime(1, B);
        record.SetDateTime(2, C);
        return record;
    }
}