.net 使用CLR将数据从Excel导入SQL Server时出错

这里是SQL DBA，不是C#或程序员.以下是我在网上找到的一些代码，它们试图适应我的需求:

public partial class StoredProcedures

{

    [Microsoft.SqlServer.Server.SqlProcedure]

    public static void ExcelTransfer(String FileName, String WorkBook, String TableName)

    {

        using (SqlConnection cn = new SqlConnection("context connection = true"))

        {

            cn.Open();

            // Connection String to Excel Workbook

            string excelConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + FileName + ";Extended Properties='Excel 12.0;HDR=YES'";

            // Create Connection to Excel Workbook

            using (OleDbConnection connection = new OleDbConnection(excelConnectionString))

            {

                OleDbCommand command = new OleDbCommand("Select Number FROM [" + WorkBook + "$]", connection);
                connection.Open();

                // Create DbDataReader to Data Worksheet

                using (DbDataReader dr = command.ExecuteReader())

                {

                    // Bulk Copy to SQL Server

                    using (SqlBulkCopy bulkCopy = new SqlBulkCopy(cn))

                    {

                        bulkCopy.DestinationTableName = TableName;

                        bulkCopy.WriteToServer(dr);

以上代码在SQL Server中注册为:

CREATE ASSEMBLY ImportFromFile_XLS
FROM '<path to .dll>'
WITH PERMISSION_SET = UNSAFE
GO

CREATE procedure readExcel (@str1 nvarchar(255), @str2 nvarchar(255), @str3 nvarchar(255))
AS
EXTERNAL NAME ImportFromFile_XLS.StoredProcedures.ExcelTransfer

当我执行的时候

EXEC dbo.readExcel 'C:\SQL_DATA\WorkBook.xls', 'WorkBook', 'testTable'

我收到错误消息:

Msg 6522, Level 16, State 1, Procedure dbo.readExcel, Line 0 [Batch Start Line 46] A .NET Framework error occurred during execution of user-defined routine or aggregate "readExcel": System.InvalidOperationException: The requested operation is not available on the context connection. System.InvalidOperationException: at System.Data.SqlClient.SqlBulkCopy.CreateOrValidateConnection(String method) at System.Data.SqlClient.SqlBulkCopy.WriteRowSourceToServerAsync(Int32 columnCount, CancellationToken ctoken) at System.Data.SqlClient.SqlBulkCopy.WriteToServer(DbDataReader reader)
at StoredProcedures.ExcelTransfer(String FileName, String WorkBook, String TableName) .

我到底做错了什么？