使用保存文件对话框将gridview数据导出到.csv

Question

我正在尝试将数据从gridview导出到.csv并使用“保存文件”对话框进行保存，但是当我按下按钮时，什么也没发生。 Gridview可以正常工作，下面是代码：

 public struct DataParameters
    {
        public List<Currency> currency;
        public string Filename;

    }

    public static DataParameters dataParameters;

单击按钮-打开文件对话框，将文件导出到csv并保存

    protected void Button1_Click(object sender, EventArgs e)
    {

        using (SaveFileDialog sfd = new SaveFileDialog() { Filter = "CSV 
files (*.csv)|*.csv|All files (*.*)|*.*" ,
            ValidateNames = true, InitialDirectory = @"C:\",
            RestoreDirectory = true, CheckFileExists = true, CheckPathExists 
= true, DefaultExt = "csv" }) {
            if (sfd.ShowDialog() == DialogResult.OK)
            {
                dataParameters.currency = GridView1.DataSource as 
List<Currency>;
                dataParameters.Filename = sfd.FileName;
            }
        }

        List<Currency> currencies = dataParameters.currency;
        string filename = dataParameters.Filename;
        using (StreamWriter sw = new StreamWriter(new FileStream(filename, 
  FileMode.Create), Encoding.UTF8))
        {
            StringBuilder sb = new StringBuilder();
            foreach (Currency c in currencies)
            {
                sb.AppendLine(string.Format($"{c.Drzava} {c.Sifra_valute} { 
{c.Valuta} {c.Jedinica} {c.Kupovni_tecaj} {c.Srednji_tecaj} 
{c.Prodajni_tecaj}"));
            }
            sw.Write(sb.ToString());
        }
    }

当我按下按钮时什么也没发生