将字符串转换为nvarchar(将excel导入mssql)

我一直在试图找到一种方法来转换数据类型字符串nvarchar，而我从excel电子表格导入数据。到目前为止，我有这段代码通过c#导入数据。

// Connection String to Excel Workbook,Replace DataSource value to point to your excel file location
    string excelConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:''Folder''Folder''Excel_File.xls ;Extended Properties=Excel 8.0";

    // Create Connection to Excel Workbook
    using (OleDbConnection connection =
                 new OleDbConnection(excelConnectionString))
    {
        OleDbCommand command = new OleDbCommand
                ("Select * FROM [Sheet1$]", connection);
        connection.Open();
        // Create DbDataReader to Data Worksheet
        using (DbDataReader dr = command.ExecuteReader())
        {
            // SQL Server Connection String
            string sqlConnectionString = "Data Source=localhost;Initial Catalog=DatabaseName;Integrated Security=True";
            // Bulk Copy to SQL Server
            using (SqlBulkCopy bulkCopy =
                       new SqlBulkCopy(sqlConnectionString))
            {
                bulkCopy.DestinationTableName = "Table_Name";
                bulkCopy.WriteToServer(dr);
                MessageBox.Show("Data Exported To Sql Server Successfully");
            }
        }

我已经寻找了从字符串转换到nvarchar的方法，但我发现的唯一示例仅用于转换从文本框或通过控制台收集的字符串。我在日期类型中确实有一列，但我在MSSQL中进行了补偿。

如果有人能给我一个我应该做的示例代码，我将不胜感激。