C# DropDownList 和 session [""]

Question

每个人。

我在从下拉列表中选择值时遇到一点问题。 当用户输入他/她的凭据并选择数据源名称时，它们都存储在 session 中。当用户稍后返回登录页面时，我希望他/她看到最后选择的数据源名称。 它是第一次工作，但是当我尝试更改数据源名称时，它不会更改，但会出现之前选择的值。你能帮我解决这个问题吗？ 谢谢!

默认.aspx

public partial class _Default : System.Web.UI.Page 
{
    private dbConnection connection = new dbConnection();
    private string[,] errorMessage = 
        { {"Expired", "Unsuccessful", "Incorrect"}, 
        {"Your Logon Session Has Expired", "Invalid Username or Password", 
            "Selected Data Source is not supported within this application"} };

    protected void Page_Load(object sender, EventArgs e)
    {

        ddlDatabase.DataTextField = "Value";
        ddlDatabase.DataValueField = "Key"; 
        ddlDatabase.DataSource = dbList.GetDbList();
        ddlDatabase.DataBind();    

        Response.Buffer = true;

        if (Session["Error"] != null)
                ErrorMessage();

        if (Session["Datasource"] != null)
            ddlDatabase.SelectedValue = Session["Datasource"].ToString();
    }

    protected void btnLogin_Click(object sender, EventArgs e)
    {
        string dataSource = ddlDatabase.SelectedValue;
        string userID = txtUserID.Text;
        string password = txtPassword.Text;

        connection = new dbConnection(dataSource, userID, password);

        if (connection.IsValid())
        {
            try
            {
                connection.GetConnection().Open();
                Session["Username"] = userID;
                Session["Password"] = password;
                Session["Datasource"] = ddlDatabase.SelectedValue;
                Response.Clear();
                Response.Redirect("main.aspx", false);
            }
            catch (Exception ex)
            {
                lblSessionInfo.Text = ex.Message;
                Session["Username"] = null;
                Session["Password"] = null;
                Session["Error"] = "Unsuccessful";
                Response.Clear();
                Response.Redirect("default.aspx");
            }
        }
        else
        {
            Session["Username"] = null;
            Session["Password"] = null;
            Session["Datasource"] = null;
            Session["Error"] = "Incorrect";
            Response.Clear();
            Response.Redirect(Request.Url.ToString(), true);
        }
    }

    protected void ErrorMessage()
    {
        int length = errorMessage.Length / 2;

        for (int i = 0; i < length; i++)
            if (Session["Error"].ToString() == errorMessage[0, i])
                lblSessionInfo.Text = errorMessage[1, i];
    }
}

main.aspx(注销)

public partial class main : System.Web.UI.Page
{
    dbConnection connection = new dbConnection();

    protected void Page_Load(object sender, EventArgs e)
    {
        Response.Buffer = true;
        if (Session["Username"] == null)
        {
            Session["Error"] = "Expired";
            Response.Clear();
            Response.Redirect("default.aspx");
        }
        else
        {
            Session["Error"] = null;
        }

        Label1.Text = Session["Datasource"].ToString();
    }
    protected void btnLogout_Click(object sender, EventArgs e)
    {
        connection.GetConnection().Close();
        Session["Username"] = null;
        Session["Password"] = null;
        Response.Clear();
        Response.Redirect(Request.Url.ToString(), true); 
    }
}

数据库列表.cs

public class dbList
{
    public static Dictionary<int, string> GetDbList()
    {
        //List<string> dataSources = new List<string>();
        var dataSources = new Dictionary<int, string>(); 

        RegistryKey reg = (Registry.LocalMachine).OpenSubKey("Software");
        reg = reg.OpenSubKey("ODBC");
        reg = reg.OpenSubKey("ODBC.INI");
        reg = reg.OpenSubKey("ODBC Data Sources");

        if (reg != null)
        {
            string[] items = reg.GetValueNames();
            Array.Sort(items);
            int i = 0;
            foreach (string item in items)
            {
                dataSources.Add(i, item);
                i++;
            }
        }

        reg.Close();

        return dataSources;
    }
}

数据库连接.cs

public class dbConnection
{
    private string[] dataSources = { "name1", "name2", "name3" };

    public dbConnection() {}

    public dbConnection(string dataSource, string userID, string password)
    {
        DataSource = dataSource;
        UserID = userID;
        Password = password;
    }

    public string DataSource { get; set; }
    private string UserID { get; set; }
    private string Password { get; set; }

    public OracleConnection GetConnection()
    {
        OracleConnection connection = null;

        string connectionString = 
            @"Data Source="+ DataSource + 
            ";User ID=" + UserID + 
            ";Password=" + Password + 
            ";Unicode=True";

        try
        {
            connection = new OracleConnection(connectionString);
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "Error");
        }

        return connection;
    }

    public bool IsValid()
    {
        int trueCount = 0;

        foreach (string dataSource in dataSources)
            if (DataSource == dataSource) trueCount++;

        if (trueCount > 0) return true;
        else  return false;
    }

}

Answer 1

更新:2011 年 6 月 13 日

你能尝试创建一个 Dictionary 吗？而不是 List<string>在你的手中 GetConnection()方法？

var dictionary = new Dictionary<int, string>();
dictionary.Add(1, "Connection1");
dictionary.Add(2, "Connection2");
dictionary.Add(3, "Connection3");
dictionary.Add(4, "Connection4");

// Binding the dictionary to the DropDownList:
dropDown.DataTextField = "Value";
dropDown.DataValueField = "Key";
dropDown.DataSource = dictionary;  //Dictionary<int, string>
dropDown.DataBind();

---

您需要先绑定(bind)“ddlDatabase”，然后设置 SelectedValue。否则，只会在您的下拉列表中创建 1 个项目(具有 SelectedValue)，并且您没有任何项目可供选择，除了一个项目。

//Code to databind ddlDatabase
BindDatabaseDropdown();
if (Session["Datasource"] != null)
        ddlDatabase.SelectedValue = Session["Datasource"].ToString();