你调用的对象是空的

Question

我收到一个关于 aspx 上传控件的错误单个 aspx 页面上的下拉列表。

这是错误...

Object reference not set to an instance of an object.

这是我的 on_submit 代码...

protected void ASPxUploadControl1_FileUploadComplete(object sender, DevExpress.Web.ASPxUploadControl.FileUploadCompleteEventArgs e)
    {
        if (e.IsValid)
        {
            string uploadDirectory = Server.MapPath("~/files/");
            //string uploadDirectory = "//DOCSD9F1/TECHDOCS/";

            string uploadFolder = DropDownList1.SelectedItem.Text;

            string fileName = e.UploadedFile.FileName;

            string path = (uploadDirectory + uploadFolder + fileName);

            e.UploadedFile.SaveAs(path);
            e.CallbackData = fileName;
        }
    }`

这是我用于创建下拉列表的代码...

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            DirectoryInfo di = new DirectoryInfo("D:/SMGUpload/SMGUpload/files");

            DropDownList1.DataSource = di.GetDirectories();

            DropDownList1.DataBind();

            foreach (DirectoryInfo i in di.GetDirectories())
            {
                DropDownList1.DataTextField = i.FullName;
                DropDownList1.DataValueField = i.FullName;
            }
        }
    }`

Answer 1

您可能想尝试以下操作：

if(!Page.IsPostBack){
    DirectoryInfo di = new DirectoryInfo("D:/SMGUpload/SMGUpload/files");
    DirectoryInfo[] diArr = di.GetDirectories();
    DropDownList1.DataSource = diArr;
    DropDownList1.DataTextField = "Name";
    DropDownList1.DataValueField = "Name";
    DropDownList1.DataBind();
}

并获取选定的值，例如：

string uploadFolder = DropDownList1.SelectedValue;

仅供参考：确保在上传文件时创建的路径中有正确的斜杠 (/)。