string path = @"C:\testdata.xlsx";
                    string excelConnectionString = string.Format("Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=\"Excel 12.0;HDR=YES\"", path);

                    
                    using (OleDbConnection connection = new OleDbConnection(excelConnectionString)) 
                    { 
                        OleDbCommand command = new OleDbCommand ("select * from [data$]", connection);
 
                        connection.Open(); 
 
                        using (DbDataReader dr = command.ExecuteReader()) // здесь все рушится

string path = @"C:\testdata.xlsx";
            string excelConnectionString = string.Format("Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=\"Excel 12.0;HDR=YES\"", path);

            using (OleDbConnection connection = new OleDbConnection(excelConnectionString))
            {
                OleDbCommand command = new OleDbCommand("select * from [data$]", connection);

                connection.Open();

                using (DbDataReader dr = command.ExecuteReader())
                {
                    string sqlConnectionString = @"Persist Security Info = false; Integrated Security = true; Initial Catalog = testdb1; server = (local)";

                    using (SqlBulkCopy bulkCopy = new SqlBulkCopy(sqlConnectionString))
                    {
                        bulkCopy.DestinationTableName = "asdf";
                        bulkCopy.WriteToServer(dr);
                    }
                }
            }