Attaching an existing but modified entity to the context (Drop-down list from Database)
Question
Experts,
Drop-down list is picking data from database and saving against the same column upon opening the web page and save the data, where saving is happening in another instead of same name,
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title></title> <script src="http://ajax.aspnetcdn.com/ajax/jquery/jquery-1.9.0.js"></script> </head> <body> <form id="form1" runat="server"> <div class="form"> <p> <asp:Label ID="Label1" runat="server" Text="Place Name" AssociatedControlID="txtName"></asp:Label> <asp:DropDownList ID="txtName" runat="server" > </asp:DropDownList> </p> <p> <asp:Label ID="Label2" runat="server" Text="Address" AssociatedControlID="txtAddress"></asp:Label> <asp:TextBox ID="txtAddress" runat="server"></asp:TextBox> </p> <p> <asp:HiddenField ID="hdnLocation" runat="server" /> </p> <p> <asp:Button ID="btnSubmit" runat="server" Text="Save" OnClick="btnSubmit_Click" /> </p> <p id="message"></p> </div> </form> <script type="text/javascript"> if (navigator.geolocation) { navigator.geolocation.getCurrentPosition(showPosition, showError); } else { $("#message").html("Geolocation is not supported by this browser."); } function showPosition(position) { var latlondata = position.coords.latitude + "," + position.coords.longitude; var latlon = "Latitude" + position.coords.latitude + "," + "Longitude" + position.coords.longitude; $("#message").html(latlon); $("[id*=hdnLocation]").val(position.coords.longitude + " " + position.coords.latitude); } function showError(error) { if (error.code == 1) { $("#message").html("User denied the request for Geolocation."); } else if (error.code == 2) { $("#message").html("Location information is unavailable."); } else if (error.code == 3) { $("#message").html("The request to get user location timed out."); } else { $("#message").html("An unknown error occurred."); } } </script> </body> </html>
using System; using System.Collections.Generic; using System.Data.Entity.Spatial; using System.Linq; using System.Web; using System.Web.UI; using System.Data.SqlClient; using System.Web.UI.WebControls; using System.Data; using System.Configuration; using System.Web.Security; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; using System.Web.Configuration; public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { if (!this.IsPostBack) { string query = "SELECT PlaceID, Name,Address FROM Placeinfo"; string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString; using (SqlConnection con = new SqlConnection(constr)) { using (SqlCommand cmd = new SqlCommand(query)) { cmd.CommandType = CommandType.Text; cmd.Connection = con; con.Open(); using (SqlDataReader sdr = cmd.ExecuteReader()) { while (sdr.Read()) { ListItem item = new ListItem(); item.Text = sdr["Name"].ToString(); txtName.Items.Add(item); txtName.ClearSelection(); } } con.Close(); } } } } public List<PlaceInfo> GetMyPlaces() { return new SampleDBEntities().PlaceInfoes.ToList(); } protected void btnSubmit_Click(object sender, EventArgs e) { PlaceInfo placeToEdit = Context.placeinfoes.Find(Convert.ToInt32(txtName.DataValueField)); using (var context = new SampleDBEntities()) { PlaceInfo placeToUpdate = context.PlaceInfoes.Find(Convert.ToInt32(txtName.DataValueField)); placeToUpdate.Name = txtName.Text; placeToUpdate.Address = txtAddress.Text; placeToUpdate.Geolocation = DbGeography.FromText("POINT( " + hdnLocation.Value + ")"); context.Entry(placeToUpdate).State = System.Data.Entity.EntityState.Modified; context.SaveChanges(); } } }
database DATABASE DISPLAY
1 answers
solution1
0 2016-11-18 20:47:44
In order to update an item in a database, we first need to make sure we'll know which one we need to reference.
First, with the creation of your DropDownList, we'll want to hide the ID of the "PlaceInfo" we are displaying. This will create the need for a "SelectMethod", and a few other adjustments:
<asp:DropDownList ID="txtName" runat="server" ItemType="PlaceInfo" DataValueField="PlaceId" DataTextField="Name" SelectMethod="GetMyPlaces"></asp:DropDownList>
The DataTextField property is the one which will display in the actual DropDown, and the DataValueField is a hidden property which we will use to reference the ID so we can call that row later.
The SelectMethod (I have as: GetMyPlaces) is the method we use to populate the DropDownList. Please excuse the brevity, as you can do this a number of ways, but essentially you want to return a list of PlaceInfos:
public List<PlaceInfo> GetMyPlaces()
{
return new SampleDbEntities().PlaceInfoes.ToList();
}
Finally - in the btnSubmit_Click method, you want to grab the row we're going to edit by using the hidden Value field from the dropdown :
PlaceInfo placeToEdit = Context.PlaceInfoes.Find(Convert.ToInt32(txtName.Value))
Assign it the new values, and tell entity framework this model is now modified:
using (var context = new SampleDBEntities())
{
PlaceInfo placeToUpdate = context.PlaceInfoes.Find(Convert.ToInt32(txtName.Value));
placeToUpdate.Name = txtName.Text;
placeToUpdate.Address = txtAddress.Text;
placeToUpdate.Geolocation = DbGeography.FromText("POINT( "+hdnLocation.Value+")");
context.Entry(placeToUpdate).State = EntityState.Modified;
context.SaveChanges();
}
Save the changes to your context and you should be good to go.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.