Question

非常简单的问题......但结果很奇怪。我只想填写c＃

中的下拉列表

protected void Page_Load(object sender, EventArgs e)
{
    if (!(Page.IsPostBack))
    {
        LoadDropDowns();            
    }
}

protected void LoadDropDowns()
{
    ddlVendor.DataSource = BL.GetAllVendors();
    ddlVendor.DataTextField = "VendorName";
    ddlVendor.DataValueField = "VendorName";
    ddlVendor.DataBind();
}

BL.GetAllVendors只是一个静态类，它可以做到这一点：

public static List<Vendor> GetAllVendors()
{
    return DL.GetAllVendors();     
}

DL.GetAllVendors也是静态类（数据层），它构建了List：

public static List<Vendor> GetAllVendors()
{
    using(SqlConnection con = new SqlConnection(connString))
    {
        //use sproc
        SqlCommand cmd = new SqlCommand("selAllVendors", con);
        cmd.CommandType = CommandType.StoredProcedure;

        //temporary storage of list of vendors
        List<Vendor> lv = new List<Vendor>();

        con.Open();
        SqlDataReader reader = cmd.ExecuteReader();

        //continue as long as we have vendors
        while (reader.Read())
        {
            //instantiate a vendor
            Vendor v = new Vendor((string)reader["VendorName"]);
            //add them to the list
            lv.Add(v);
        }
        //clean the reader
        reader.Close();
        reader = null;

        //return that list
        return lv;
    }
}

供应商类很简单：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for Vendor
/// </summary>
namespace TK.Objects
{
    public class Vendor
    {
        private string VendorName { get; set; }

        public Vendor(string vn)
        {
            VendorName = vn;
        }
    }
}

我知道我的sproc是正确的，因为我做了调试/监视，我看到它取消了两个记录“All”和“Microsoft”。

简单来说：

CREATE PROCEDURE selAllVendors
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

      SELECT
        Vendor AS VendorName,
        1 as SortOrder
    FROM 
        Vendor
    UNION ALL
    SELECT
        'All' AS VendorName,
        0 as SortOrder
    ORDER BY 
        SortOrder,
        Vendor  
END
GO

但是当我运行此代码时出现错误：

System.Web.HttpException was unhandled by user code
  Message=DataBinding: 'TK.Objects.Vendor' does not contain a property with the name 'VendorName'.
  Source=System.Web
  ErrorCode=-2147467259
  WebEventCode=0
  StackTrace:
       at System.Web.UI.DataBinder.GetPropertyValue(Object container, String propName)
       at System.Web.UI.DataBinder.GetPropertyValue(Object container, String propName, String format)
       at System.Web.UI.WebControls.ListControl.PerformDataBinding(IEnumerable dataSource)
       at System.Web.UI.WebControls.ListControl.OnDataBinding(EventArgs e)
       at System.Web.UI.WebControls.ListControl.PerformSelect()
       at System.Web.UI.WebControls.BaseDataBoundControl.DataBind()
       at _Default.LoadDropDowns() in c:\Users\Documents\Visual Studio 2010\WebSites\T\Default.aspx.cs:line 26
       at _Default.Page_Load(Object sender, EventArgs e) in c:\Users\Documents\Visual Studio 2010\WebSites\T\Default.aspx.cs:line 17
       at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)
       at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
       at System.Web.UI.Control.OnLoad(EventArgs e)
       at System.Web.UI.Control.LoadRecursive()
       at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
  InnerException:

我在这里缺少什么？

Answer 1

VendorName课程中的Vendor属性必须是公开的，而不是私有的。

Answer 2

更改供应商类属性

private string VendorName { get; set; }

到

public string VendorName { get; set; }

你应该都很好。

Answer 3

您可以将此代码用于类供应商。

public class Vendor
{
    private string vendorName = string.Empty; 

    public string VendorName
    {
        get { return vendorName; }
        set { vendorName = value; }
    }

    public Vendor(string vn)
    {
        VendorName = vn;
    }
}

加载ASP.NET DropDownList

3 个答案: