how can we achieve that :-sublist in parents listview but in taaped next page.
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shiwam
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//////////////////////////////Model/////////////////////////////////////
public class ClassInfos
{
[PrimaryKey, AutoIncrement]
public int ClassId { get; set; }
public string ClassName { get; set; }}
public class StudentInfo
{
[PrimaryKey, AutoIncrement]
public int StudentId { get; set; }
public int Classid { get; set; }
public string studentName { get; set; }}
/////////////////////////first page////////////////////////////////////////////////////////////
public SQLiteConnection conn;
public MainPage()
{
InitializeComponent();
using (conn = new SQLiteConnection(App.Database))
{
conn.CreateTable();
var data = conn.Table().OrderBy(c => c.ClassId).ToList();Datalist.ItemsSource = data; } } public void AddButton_Clicked(object sender, EventArgs e) { if (ClassEntry.Text == null) { DisplayAlert(null, "Null Value", "Ok"); } else { using (conn = new SQLiteConnection(App.Database)) { conn.CreateTable<ClassInfos>(); ClassInfos classinfo = new ClassInfos { ClassName = ClassEntry.Text }; conn.Insert(classinfo); DisplayAlert(classinfo.ClassName, "Saved", "Ok"); Navigation.PopToRootAsync(); ClassEntry.Text = ""; } } }///////////////////////////////////Second Page///////////////////
SQLiteConnection conn;
ClassInfos Info;
public StudentList(ClassInfos Infos)
{
InitializeComponent();
this.Info = Infos;
}private void AddButton_Clicked(object sender, EventArgs e) { if (StudentEntry.Text == null) { DisplayAlert(null, "Null Value", "Ok"); } else { try { using (conn = new SQLiteConnection(App.Database)) { StudentInfo std = new StudentInfo(); std.studentName = StudentEntry.Text; std.Classid = Info.ClassId;///here assigning the parents id to Student TAble conn.CreateTable<StudentInfo>(); conn.Insert(std); } StudentEntry.Text = ""; } catch(Exception ex) { DisplayAlert("Message", ex.Message, "Ok"); } } } protected override void OnAppearing() { base.OnAppearing(); try { using (conn = new SQLiteConnection(App.Database)) { var data = conn.Table<StudentInfo>().Where(c => c.Classid == Info.ClassId);//Getting the child Studentlist.ItemsSource = data; } } catch (Exception ex) { DisplayAlert("Message",ex.Message , "Ok"); } } }0
Answers
When you're clicking the item and navigating to the other page, pass the subcollection as the argument through the constructor of your ViewModel/View, depending on how you do the navigation.
Here my code & i'm doing it by passing parents id to the next page & i am confused with onetomany relationship here ...from this code i can add only one children in respected parents & if i try to add other children then previous one get overwrite bye new One.
Sir plz help me i am a beginner
//////////////////////////////Model/////////////////////////////////////
public class ClassInfos { [PrimaryKey,AutoIncrement] public int ClassId { get; set; } public string ClassName { get; set; } [OneToMany(CascadeOperations = CascadeOperation.All)] public List<StudentInfo> Students { get; set; } } public class StudentInfo { [PrimaryKey, AutoIncrement] public int StudentId { get; set; } [ForeignKey(typeof(ClassInfos))] public int Classid { get; set; } // [ManyToOne] // public ClassInfos User { get; set; } public string studentName { get; set; } }//////////////////////////////////////////////////////////AddClass.cs Page/////////////////////////////////////////////////////////////
public void AddButton_Clicked(object sender, EventArgs e) { if (ClassEntry.Text == null) { DisplayAlert(null, "Null Value", "Ok"); } else { using (conn = new SQLiteConnection(App.Database)) { ClassInfos classinfo = new ClassInfos(); classinfo.ClassName = ClassEntry.Text; conn.CreateTable<ClassInfos>(); conn.Insert(classinfo); DisplayAlert(classinfo.ClassName, "Saved", "Ok"); Navigation.PopToRootAsync(); ClassEntry.Text = ""; } } } protected override void OnAppearing() { base.OnAppearing(); using (conn = new SQLiteConnection(App.Database)) { conn.CreateTable<ClassInfos>(); var data = conn.Table<ClassInfos>().OrderBy(c => c.ClassId).ToList(); Datalist.ItemsSource = data; } } public void Datalist_ItemTapped(object sender, ItemTappedEventArgs e) { ClassInfos details = e.Item as ClassInfos; Navigation.PushAsync(new StudentList(details.ClassId)); }////////////////////////////////////////////////Studentlist.cs page ///////////////////////////////////////////////////////////
public SQLiteConnection conn; readonly private int classId; // public ClassInfos clssinfo; public StudentList(int classId) { InitializeComponent(); this.classId = classId; } private void AddButton_Clicked(object sender, EventArgs e) { if (StudentEntry.Text == null) { DisplayAlert(null, "Null Value", "Ok"); } else { conn = new SQLiteConnection(App.Database); conn.CreateTable<StudentInfo>(); StudentInfo studentinfo = new StudentInfo() { studentName = StudentEntry.Text, }; var data =conn.Table<ClassInfos>(); int id = Convert.ToInt32(classId); var data1 = (from values in data where values.ClassId == id select values).Single(); data1.Students = new List<StudentInfo>();// { studentinfo }; conn.Insert(studentinfo); data1.Students.Add(studentinfo); conn.UpdateWithChildren(data1); //var data2 = conn.GetWithChildren<ClassInfos>(data1.ClassId, recursive: true); // conn.GetWithChildren<StudentInfo>(studentinfo.StudentId, recursive: true); StudentEntry.Text = ""; } } protected override void OnAppearing() { base.OnAppearing(); conn = new SQLiteConnection(App.Database); int id = Convert.ToInt32(classId); List<StudentInfo> list = conn.GetAllWithChildren<StudentInfo>().Where(c => c.Classid == id).ToList(); Studentlist.ItemsSource =list; } }plz help me with small demo
Pass the list(not classid) to the next page .
First Page
public void Datalist_ItemTapped(object sender, ItemTappedEventArgs e) { ClassInfos details = e.Item as ClassInfos; Navigation.PushAsync(new StudentList(details.Students)); }Second Page
public StudentList( List<StudentInfo> stu) { InitializeComponent(); this.Stu= stu; Studentlist.ItemsSource =stu; }sir i have tried but not getting the children .Sir Give me full demonstration of this cause my whole project depend upon this so sir plz.
Here's my UI & code:-
SQLiteConnection conn; List<StudentInfo> Stu; public StudentList(List<StudentInfo> stu) { InitializeComponent(); this.Stu = stu; Studentlist.ItemsSource =stu; } private void AddButton_Clicked(object sender, EventArgs e) { if (StudentEntry.Text == null) { DisplayAlert(null, "Null Value", "Ok"); } else { conn = new SQLiteConnection(App.Database); conn.CreateTable<StudentInfo>(); StudentInfo std = new StudentInfo() { studentName = StudentEntry.Text, }; conn.Insert(std); Stu.Add(std); StudentEntry.Text = ""; } } }Add breakpoint on
ClassInfos details = e.Item as ClassInfos;in item tap event to see if details null or not.everything seems fine up to this .. details is null & while navigating it passing the information to next page but
in the execution process of
Stu.Add(std);
it throw exception Unhandled i.e object is not set to an instance of an object.
The problem is the rendering/binding on the First page , not the parameter passed to second page .
Try to move the code into
ItemSelectedinstead ofItemTappedon ListView.<ListView ItemSelected="ListView_ItemSelected"/> private void ListView_ItemSelected(object sender, SelectedItemChangedEventArgs e) { ClassInfos details = e.SelectedItem as ClassInfos; Navigation.PushAsync(new StudentList(details.ClassId)); }nothing happening ...it doesn't even navigate to next page by ItemSelected method by calling Navigating function ..& i don't know why...
> Try to move the code into ItemSelected instead of ItemTapped on ListView.
>
> <ListView ItemSelected="ListView_ItemSelected"/> private void ListView_ItemSelected(object sender, SelectedItemChangedEventArgs e) { ClassInfos details = e.SelectedItem as ClassInfos; Navigation.PushAsync(new StudentList(details.ClassId)); }
Nothing changed still same error i.e
object is not set to an instance of an object at Stu.Add(std);
Hi if possible could you provide me a basic mini project to test ?
Just zip the project and attach in the comment .
sir here's zip file the method i tried before i.e passing the id to the next page & bye this method & i can bind the data on First page but only one student i can able to add in respected items.
According to my thought :-
""i even tried your method & the subcollection i.e details.Students passing that as args in next page But if i am only passing the List then how can 2nd page know that this subcollection belong to that respected parents id cause for next page "List Stu" is just as a new List Stu for next page which has no parents detail .... & dont even know that it belongs to ClassInfos Table as Children For that i tried by passing two parameter "details.Students & details.Id" to the next page & assign the list Stu to the table ClassInfo by the help of details.id & assign to that ClassInfos.Students." But it don't work so I came back to my previous code & which i have already attached.
@ColeX sir help me with this
There are some points needs to notice in your sample
Create Table for
StudentInfo.Insert data for StudentInfo table .
Relate StudentInfo with ClassInfos .
Details check
https://www.codejourney.net/2017/05/sqlite-net-extensions-one-to-many-relationships/
https://github.com/jsuarezruiz/Xamarin.Forms-Samples/tree/master/TodoSqlite Multiple Tables
i did the same things before ..i am already gone through that site...& i am doing the same things but problem is i can only able to add one children ..& when insert next children to the respected parents (suppose now studentid is 1 & name is Stefan & when i insert next student as Ram the studentid=2 & Name is =Ram ..it show up in list view but prevoius name Stefan is gone from listview it only show Ram.)problem is How can i retrive all the student from that respected parents in list view..
Sir Just for once Watch it from up to down & give me idea to retrive the all the children.
protected override void OnAppearing()
{
base.OnAppearing();
using (conn = new SQLiteConnection(App.Database))
{
// var datas = conn.Table().Where(c => c.ClassId == classId);
// var data = (from values in datas where values.ClassId == classId select values).Single();
//IEnumerable<List> result = datas.Select(x => x.Students);
// Studentlist.ItemsSource = result;
conn = new SQLiteConnection(App.Database);
var list= conn.Table().Where(c => c.Classid == classId).ToList();
Studentlist.ItemsSource = list;
// List list = conn.GetAllWithChildren().Where(c => c.Classid == id).ToList();
/// Studentlist.ItemsSource =list;
}
i have used this method to retrive all the children but i failed it only return one children which is last inserted to the list.& previous one get overwrite in view.
List list = conn.GetAllWithChildren().ToList();
I've tried this already but i dont know why it only retrive the data which is last inserted & previous data is lost.There's always one child only i can add.I am doing mistake while retriving the data but i don't have idea .
It is weird ,
conn.GetAllWithChildren().ToList();returns all the student i added .ya it returns all the children but all the children populate in every parents so i did linq operation by matching the children foreign key with parents id to get the child of respected parents.
var datas = conn.GetAllWithChildren<StudentInfo>().ToList(); var data = (from stds in datas where stds.Classid == Parents.ClassId select stds).ToList(); Studentlist.ItemsSource = data;though it won't work I have already tried each & everything You said me till now.So i come to the discussion page..But every logic i used to retrive i failed
I think problem is with ForeignKey..it only assign to the one item at a time.After inserting next subitem then previous ForeignKey value of subitem becomes 0.
I did it now but without subcollection in model
//////////////////////////////Model/////////////////////////////////////
public class ClassInfos
{
[PrimaryKey, AutoIncrement]
public int ClassId { get; set; }
public string ClassName { get; set; }
public class StudentInfo
{
[PrimaryKey, AutoIncrement]
public int StudentId { get; set; }
public int Classid { get; set; }
public string studentName { get; set; }
/////////////////////////first page////////////////////////////////////////////////////////////
public SQLiteConnection conn;
public MainPage()
{
InitializeComponent();
using (conn = new SQLiteConnection(App.Database))
{
conn.CreateTable();
var data = conn.Table().OrderBy(c => c.ClassId).ToList();
Datalist.ItemsSource = data; } } public void AddButton_Clicked(object sender, EventArgs e) { if (ClassEntry.Text == null) { DisplayAlert(null, "Null Value", "Ok"); } else { using (conn = new SQLiteConnection(App.Database)) { conn.CreateTable<ClassInfos>(); ClassInfos classinfo = new ClassInfos { ClassName = ClassEntry.Text }; conn.Insert(classinfo); DisplayAlert(classinfo.ClassName, "Saved", "Ok"); Navigation.PopToRootAsync(); ClassEntry.Text = ""; } } }///////////////////////////////////Second Page///////////////////
SQLiteConnection conn;
ClassInfos Info;
public StudentList(ClassInfos Infos)
{
InitializeComponent();
this.Info = Infos;
}
private void AddButton_Clicked(object sender, EventArgs e) { if (StudentEntry.Text == null) { DisplayAlert(null, "Null Value", "Ok"); } else { try { using (conn = new SQLiteConnection(App.Database)) { StudentInfo std = new StudentInfo(); std.studentName = StudentEntry.Text; std.Classid = Info.ClassId;///here assigning the parents id to Student TAble conn.CreateTable<StudentInfo>(); conn.Insert(std); } StudentEntry.Text = ""; } catch(Exception ex) { DisplayAlert("Message", ex.Message, "Ok"); } } } protected override void OnAppearing() { base.OnAppearing(); try { using (conn = new SQLiteConnection(App.Database)) { var data = conn.Table<StudentInfo>().Where(c => c.Classid == Info.ClassId);//Getting the child Studentlist.ItemsSource = data; } } catch (Exception ex) { DisplayAlert("Message",ex.Message , "Ok"); } } }