Question

我有一个文本框，其值会进入按钮单击的下拉列表。问题是当我填写所有数据并提交表格时。当我第二次看到这个价值时，它会从下拉列表中消失。我该怎么做才能使值在下拉修复中得到。请参阅代码供您参考：

 <tr>
        <td class="td">Location/City</td>
        <td>
            <asp:DropDownList CssClass="txtfld-popup" ID="ddlLocation" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ddlLocation_SelectedIndexChanged"></asp:DropDownList>
            <asp:RequiredFieldValidator CssClass="error_msg" ID="reqLocation" ControlToValidate="ddlLocation" runat="server" ErrorMessage="Please enter location" InitialValue="--Select--" SetFocusOnError="true"></asp:RequiredFieldValidator>
        </td>
    </tr>
    <tr>
        <td>
            <asp:TextBox ID="txtOtherCity" runat="server" Visible="false" CssClass="txtfld-popup"></asp:TextBox>
            &nbsp;&nbsp;&nbsp;
                    <asp:Button ID="btnAddDropDown" runat="server" Width="63" Text="Add" CausesValidation="false" OnClick="btnAddDropDown_Click1" />

        </td>
    </tr>

另外，请参阅后面的代码供您参考： -

 protected void ddlLocation_SelectedIndexChanged(object sender, EventArgs e)
{
    if (ddlLocation.SelectedItem.Text == "Other")
    {
        txtOtherCity.Visible = true;
    }
    else
    {
        txtOtherCity.Visible = false;
    }
}
protected void btnAddDropDown_Click1(object sender, EventArgs e)
{
    string city = txtOtherCity.Text.Trim();
    if (!string.IsNullOrEmpty(city))
    {
        ddlLocation.Items.Add(new ListItem(city, city));
    }
}

Answer 1

您必须将文本框中的值存储到数据库中的表dbo.Cities中。下次当您返回同一页面时，下拉列表将从db获取数据。

Answer 2

然后在btnAddDropDown_Click1()上，您应该将“txtOtherCity”TextBox中的城市值插入相应的表格，然后再次绑定城市的DropDown。喜欢的东西

 protected void btnAddDropDown_Click1(object sender, EventArgs e)
        {
          string strconnection =            System.Configuration.ConfigurationManager.AppSettings["YourConnectionString"].ToString();
            string city = txtOtherCity.Text.Trim();
            DataSet ds=new DataSet();
            if (!string.IsNullOrEmpty(city))
            {
                // Your code to insert the value of the city from the 'txtOtherCity'           `TextBox` to the respective table
                 //Edit: this is a very rudimentary code
                 string query = "INSERT INTO Career.Location (State) " + 
                       "VALUES (@city) ";

        // create connection and command
          using(SqlConnection cn = new SqlConnection(strconnection))
          using(SqlCommand cmd = new SqlCommand(query, cn))
           {
            // define parameters and their values
            cmd.Parameters.Add("@city", SqlDbType.VarChar, 50).Value = city;

            // open connection, execute INSERT, close connection
            cn.Open();
            cmd.ExecuteNonQuery();
            cn.Close();

            }
            query = "select State from Career.Location";
            using(SqlConnection cnn = new SqlConnection(strconnection))
            using(SqlCommand cmdd = new SqlCommand(query, cnn))
           {  
            SqlDataAdapter adp = new SqlDataAdapter(cmdd);            
            cnn.Open();
            adp .Fill(ds);
            cnn.Close();

            }
             ddlLocation.DataSource=ds;
             ddlLocation.DataTextField = "State";
             ddlLocation.DataValueField = "State";
             ddlLocation.DataBind();
            }
        }

Answer 3

您是否具有在数据库中插入数据的功能（不仅在下拉列表中添加新项目）。您必须在适当的表格中插入城市才能在以后查看。

实施取决于您的架构，DAL的实施等。例如 - 如果您使用的是ADO.NET，则可以使用存储过程在表中插入值：

CREATE PROCEDURE Add_City @CityName varchar(50), @StateID int AS BEGIN INSERT INTO dbo.Cities (CityName, StateID) values (@CityName, @StateID) END GO

然后从应用程序中调用它。这样的事情：

using (SqlConnection con = new SqlConnection("the connection string"))
        {

            SqlCommand cmd = new SqlCommand();

            cmd.CommandType = CommandType.StoredProcedure;

            cmd.CommandText = "Add_City";

            cmd.Parameters.Add("@CityName", SqlDbType.VarChar).Value = txtCity.Text.Trim();

            cmd.Parameters.Add("@StateID", SqlDbType.Int).Value = CountryId;

            cmd.Connection = con;

            try
            {

                con.Open();

                cmd.ExecuteNonQuery();

                // lblMessage.Text = "City inserted successfully!";

            }

            catch (Exception ex)
            {

                throw ex; // Or log or handle somehow the exception

            }

        }

Answer 4

我得到了这个解决方案的答案，请参阅代码供您参考： -

protected void BindContrydropdown()
{
    //conenction path for database
    //string connection = WebConfigurationManager.ConnectionStrings["myconn"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constring))
    {
        con.Open();
        SqlCommand cmd = new SqlCommand("Select Id,CityName From Career.Location", con);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        ddllocation1.DataSource = ds;
        ddllocation1.DataTextField = "CityName";
        ddllocation1.DataValueField = "Id";
        ddllocation1.DataBind();
        ddllocation1.Items.Insert(0, new ListItem("--Select--", "0"));
        ddllocation1.Items.Insert(1, new ListItem("--OTHER--", "0"));
        con.Close();
    }
}
protected void ddllocation1_SelectedIndexChanged(object sender, EventArgs e)
{

    string country = "India";

    var cities = _helper.GetLocations(country, ddllocation1.SelectedValue);
    cities.Insert(0, "--Select--");
    cities.Insert(1, "Other");
    ddlLocation.DataSource = cities;
    ddlLocation.DataBind();

}
protected void btnAddDropDown_Click1(object sender, EventArgs e)
{
    using (SqlConnection con = new SqlConnection(constring))
    {
        con.Open();
        //BindContrydropdown();
        //if (txtOtherCity.Text != "")
        //{

        //    txtOtherCity.Text = "";
        //}
        SqlCommand cmd = new SqlCommand();
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.CommandText = "Add_CityforLocation";
        cmd.Parameters.Add("@ID", SqlDbType.VarChar).Value = 0;
        cmd.Parameters.Add("@CountryName", SqlDbType.VarChar).Value = "India";
        cmd.Parameters.Add("@CityName", SqlDbType.VarChar).Value = txtOtherCity.Text.Trim();
        cmd.Parameters.Add("@StateName", SqlDbType.VarChar).Value = ddlLocation.SelectedItem.ToString();
        cmd.Connection = con;
        try
        {
            // con.Open();
            cmd.ExecuteNonQuery();
            BindContrydropdown();
            // lblMessage.Text = "City inserted successfully!";
        }
        catch (Exception ex)
        {
            Response.Write(ex.Message);//You Can Haave Messagebox here
        }
        finally
        {
            con.Close();
        }
    }
}

另见下拉列表的html： -

<tr>
        <td class="td">Location/State</td>
        <td>
            <asp:DropDownList CssClass="txtfld-popup" ID="ddllocation1" OnSelectedIndexChanged="ddllocation1_SelectedIndexChanged" runat="server" AutoPostBack="true"></asp:DropDownList>
            <asp:RequiredFieldValidator CssClass="error_msg" ID="RequiredFieldValidator1" ControlToValidate="ddllocation1" runat="server" ErrorMessage="Please enter location" InitialValue="--Select--" SetFocusOnError="true"></asp:RequiredFieldValidator>
        </td>
    </tr>
    <tr>
        <td class="td">Location/City</td>
        <td>
            <asp:DropDownList CssClass="txtfld-popup" ID="ddlLocation" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ddlLocation_SelectedIndexChanged"></asp:DropDownList>
            <asp:RequiredFieldValidator CssClass="error_msg" ID="reqLocation" ControlToValidate="ddlLocation" runat="server" ErrorMessage="Please enter location" InitialValue="--Select--" SetFocusOnError="true"></asp:RequiredFieldValidator>
        </td>
    </tr>
    <tr>
        <td>
            <asp:TextBox ID="txtOtherCity" runat="server" Visible="false" CssClass="txtfld-popup"></asp:TextBox>
            &nbsp;&nbsp;&nbsp;
                    <asp:Button ID="btnAddDropDown" runat="server" Width="63" Text="Add" CausesValidation="false" OnClick="btnAddDropDown_Click1" />
        </td>
    </tr>

这解决了我，另请参阅存储过程： -

Alter PROCEDURE [dbo].[Add_CityforLocation]
-- Add the parameters for the stored procedure here
@ID int,
@CountryName nvarchar(100),
@StateName nvarchar(100),
@CityName varchar(100)

AS 开始 INSERT INTO Career.Location（CountryName，StateName，CityName）值（@ CountryName，@ StateName，@ CityName）结束 GO

提交后，下拉值消失

4 个答案: