Dynamically created button refreshes the page instead of doing as due

Evgenie Tivaniuk

I am slowly getting into ASP.NET, currently trying to make a small webforms app for a hackathon.

The page that I am having problems with is supposed to show a list of companies to which person can apply. Since the list of those companies can change, company always can be added or removed, I want to make some kind of table which loads values dynamically.

The table appears when a user clicks "View all companies", it shows a table with each row including the name of company and a button to move to the page of this company. At this stage, I am trying to make something even more simple, for the sake of testing. So, the button should just display some kind of text.

But here's the problem. When I click on the button, it just resets the page and as I understand, runs "Page_Load". The text is also resets to the value from Page_Load.

Now, I'll try to give code and try to give the best descriptions.

Here's the Page_Load, it just displays the name of the user, and hides the table with company names.

protected void Page_Load(object sender, EventArgs e)
{
if (thisUser == null)
lblWelcomeUser.Text = "Welcome";
else
lblWelcomeUser.Text = "Welcome, " + thisUser.FirstName + " " + thisUser.LastName;
pnlCompaniesView.Visible = false;
}

The code for showing all companies comes here:

protected async void btnViewAllCompanies_Click(object sender, EventArgs e)
{
ResetCompaniesTable();
lblWelcomeUser.Text = "ViewAll";
FirebaseResponse response = await HRGlobalHub.Code.Start.Firebase.thisFirebaseClient.GetTaskAsync("HRGlobalHub/Database/Companies/CompaniesList/");
HRGlobalHub.Code.Company.CompaniesNamesList thisData = response.ResultAs();
string[] CompanyArray = thisData.CompanyNameListVar.Split(',');
for (int i = 1; i < CompanyArray.Length; i++)
{
response = await HRGlobalHub.Code.Start.Firebase.thisFirebaseClient.GetTaskAsync("HRGlobalHub/Database/Companies/CompaniesDatabase/" + CompanyArray[i]);
HRGlobalHub.Code.Company.Company result = response.ResultAs();
tbtTestTable.Rows.Add(NewCompanyRow(result));
}
pnlCompaniesView.Visible = true;
pnlCompaniesView.Width = 1100;
tbtTestTable.Width = 1100;
lblWelcomeUser.Text = tbtTestTable.Visible.ToString();
}

It loads first just the names of companies, then full companies data from the server. Each company turns into a table row. This part works so far. As you can see, the button_click also should get the Company that is in use.:

public TableRow NewCompanyRow(HRGlobalHub.Code.Company.Company thisCompany)
{
TableRow newRow = new TableRow();
Button btnApply = new Button();
btnApply.Text = "Apply";
btnApply.Click += (sender, EventArgs) => { btnApplyClick(sender, EventArgs, thisCompany); };
TableCell Cell0 = new TableCell();
TableCell Cell1 = new TableCell();
Cell0.Text = thisCompany.Name;
Cell1.Controls.Add(btnApply);
Cell0.Width = 150;
Cell1.Width = 150;
newRow.Cells.Add(Cell0);
newRow.Cells.Add(Cell1);
btnApply.Width = 150;
return newRow;
}

Again, since it's just testing stage for this page, the button should only display the name of the company that it gets as variable.

void btnApplyClick(Object sender, EventArgs e, HRGlobalHub.Code.Company.Company thisCompany)
{
lblWelcomeUser.Text = "Apply to " + thisCompany.Name;
}

And here is the problem: instead of doing what appears in the method, it just resets the page. And it doesn't matter what I try to do, display a text, go to another page, change a variable, save data to server, it doesn't work.

I spent two days trying to solve it, was actively googling. Tried using static variables in same class, and in another one, tried saving data to server, trying declaring button as global variables in the relevant window class.

If I declare just one button as global class variable, then assign it to the table, it does work, but only with just one button involved. With two of them, the code always goes for the last one.

Many of my searches for solutions, and the only answer I got from Stack Overflow was to use something called "PostBack", but I still can't understand what it is, and how to use it.

As I understand, the idea is to run the required method at Page Load. But how I can make sure that the relevant method is used? All my attempts to store the data failed: global variables are reset, and any attempts to use buttons to store the data on server on another class, completely failed.

I tried following:

async void btnApplyClick(Object sender, EventArgs e, HRGlobalHub.Code.Company.Company thisCompany)
{
var newMI = new HRGlobalHub.Code.MainInterface.MI
{
Id = "MI",
Action = "Apply",
IsEmpty = false,
UsedCompanyName = thisCompany.Name
};
SetResponse response = await HRGlobalHub.Code.Start.Firebase.thisFirebaseClient.SetTaskAsync("HRGlobalHub/MI/" + newMI.Id, newMI);
}

I hoped to load the MI at age Load, but as was expected, the method simply doesn't run.

I tried to create Lists of button variables then trying to change them at the stage when table is created. I didn't save exact code, but it was something lie:

Buttons.Add(new Button());
Buttons[Buttons.Count-1].Text = "Apply";
Buttons[Buttons.Count-1].Click += (sender, EventArgs) => { btnApplyClick(sender, EventArgs, thisCompany);};

I guess, I can use the dumb method and instead of using dynamic buttons create a table with 1000 of them, and set an own void to each, then hide empty lines, but this isn't really the solution, it's a way to go around it, and quite silly one.

Please help, I can't solve it on my own.

Thank you,

Evgenie

6 Replies

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Evgenie Tivaniuk5y ago
Solved it myself after all. In the end, the error was, that the dynamically created buttons also had to exist\be created at Page Load. So, I added the void for creating table with buttons at the Page Load, and just turned it invisible.

Here's where I found out about this:
https://stackoverflow.com/questions/6356489/commandeventargs-and-event-question

However that started causing problems with buttons that needs to transit to another page. So, I added one more variable that is also checked at Page Load. If it is false, the Page works usually, if true then it moves to another page.
protected void Page_Load(object sender, EventArgs e)
{
    HRGlobalHub.Code.Start.Firebase.thisFirebaseClient = new FireSharp.FirebaseClient(HRGlobalHub.Code.Start.Firebase.thisFirebaseConfig);

    pnlCompaniesView.Visible = false;

    if (!IsPostBack)
    {
        if (thisUser == null)
            lblWelcomeUser.Text = "Welcome";
        else
            lblWelcomeUser.Text = "Welcome, " + thisUser.FirstName + " " + thisUser.LastName;
    }

    else if (Transit == true)
    {
        HRGlobalHub.Pages.Company.CreateCompany.thisUser = thisUser;
        Server.Transfer("/Pages/Company/CreateCompany.aspx", false);
    }

    else if(Transit == false)
    {
            btnViewAllCompanies_Click(this, e);
            pnlCompaniesView.Visible = false;
    }
}
Buttons are created as before, no changes here:
Button btnApply = new Button();
btnApply.Text = "Apply";
btnApply.Click += (sender, EventArgs) => { btnApplyClick(sender, EventArgs, thisCompany); };
And the button that should transit to an other page, just changes the variable value:
protected void btnCreateCompany_Click(object sender, EventArgs e)
{
    Transit = true;
}
Evgenie Tivaniuk5y ago
About the code you propose. So, there should be two methods, one for Command and one for Click? But where I actually invoke the Command?
btnApply.Click += new EventHandler(btnApplyClick);
btnApply.CommandArgument = thisCompany.Name;

void btnApply_Command(object sender, CommandEventArgs e)
{
    string Name = e.CommandArgument.ToString();
}

void btnApplyClick(Object sender, EventArgs e)
{
    lblWelcomeUser.Text = "Apply to "+gCompany.Name;
}
I tried using:
btnApply.Click += new EventHandler(btnApply_Command);
But this doesn't work.

I am really sorry, all this must sound noob-ish to those who are past it, but I can't get through this alone.
Evgenie Tivaniuk5y ago
I did try some more research and testing, and that's what I am using now:

Here's the Page_Load, on first load it just displays the name of the user, and hides the table with company names. On non-first load, it should run click button events.
protected void Page_Load(object sender, EventArgs e)
{
    HRGlobalHub.Code.Start.Firebase.thisFirebaseClient = new FireSharp.FirebaseClient(HRGlobalHub.Code.Start.Firebase.thisFirebaseConfig);

    pnlCompaniesView.Visible = false;

    if (!IsPostBack)
    {
        if (thisUser == null)
            lblWelcomeUser.Text = "Welcome";
        else
            lblWelcomeUser.Text = "Welcome, " + thisUser.FirstName + " " + thisUser.LastName;

        gCompany = new Code.Company.Company();
    }

    else
    {
        if (Action=="Apply")
            btnApplyClick(this, e);
        else if (Action == "Suggest")
            btnSuggestClick(this, e);
        if (Action == "View")
            btnViewClick(this, e);
    }
}
This part loads first just the names of companies, then full companies data from the server. Each company turns into a table row. It also creates OnClientClick button events, that should load on non-first Page Load.
public TableRow NewCompanyRow(HRGlobalHub.Code.Company.Company thisCompany)
{
    TableRow newRow = new TableRow();

    Button btnApply = new Button();
    btnApply.Text = "Apply";
    btnApply.OnClientClick +=  gCompany = thisCompany;
    btnApply.OnClientClick += Action = "Apply";

    Button btnSuggest = new Button();
    btnSuggest.Text = "Suggest";
    btnSuggest.OnClientClick += gCompany = thisCompany;
    btnSuggest.OnClientClick += Action = "Suggest";


    Button btnView = new Button();
    btnView.Text = "View";
    btnView.OnClientClick += gCompany = thisCompany;
    btnView.OnClientClick += Action = "View";

    TableCell[] Cells = new TableCell[6];

    for (int i = 0; i < Cells.Length; i++)
        Cells[i] = new TableCell();

    Cells[0].Text = thisCompany.Name;
    Cells[1].Text = thisCompany.FieldOfWork;
    Cells[2].Text = thisCompany.Employees.Count.ToString();
    Cells[3].Controls.Add(btnView);
    Cells[4].Controls.Add(btnApply);
    Cells[5].Controls.Add(btnSuggest);

    for (int i = 0; i < Cells.Length; i++)
        Cells[i].Width = 150;

    newRow.Width = 900;

    for (int i = 0; i < Cells.Length; i++)
        newRow.Cells.Add(Cells[i]);

    btnApply.Width = 150;
    btnSuggest.Width = 150;
    btnView.Width = 150;

    return newRow;
}
Again, since it's just testing stage for this page, the button should only display the name of the company that it gets as variable.
void btnApplyClick(Object sender, EventArgs e, HRGlobalHub.Code.Company.Company thisCompany)
{
    lblWelcomeUser.Text = "Apply to " + thisCompany.Name;
}
This works but only partly: whatever I try the code from Page Load always runs the last "mentioned" Action (which is "View") and always goes for the company from the last row.
Sachin Singh5y ago
why don't you use command argument
btnApply.Click += =new EventHandler(button_Click);
btnApply.CommandArgument = thisCompany.Name;

void btnApply_Command(object sender, CommandEventArgs e)
{
     string Name= e.CommandArgument.ToString();
}
Evgenie Tivaniuk5y ago
I just tried it, it no longer resets the page text, but neither it shows text as the button should make it.

After pressign the Apply button, the text should show "Apply to " +Company.Name
protected void Page_Load(object sender, EventArgs e)
{
    HRGlobalHub.Code.Start.Firebase.thisFirebaseClient = new FireSharp.FirebaseClient(HRGlobalHub.Code.Start.Firebase.thisFirebaseConfig);

    if (!IsPostBack)
    {
        if (thisUser == null)
            lblWelcomeUser.Text = "Welcome";
        else
            lblWelcomeUser.Text = "Welcome, " + thisUser.FirstName + " " + thisUser.LastName;

        pnlCompaniesView.Visible = false;
    }
}
Button btnApply = new Button();
btnApply.Text = "Apply";
btnApply.Click += (sender, EventArgs) => { btnApplyClick(sender, EventArgs, thisCompany);};
void btnApplyClick(Object sender, EventArgs e, HRGlobalHub.Code.Company.Company thisCompany)
{
    lblWelcomeUser.Text = "Apply to "+thisCompany.Name;
}
I also tried moving to another page on button click, but this also doesn't work.
void btnApplyClick(Object sender, EventArgs e, HRGlobalHub.Code.Company.Company thisCompany)
{
    Server.Transfer("User/UserSignUp.aspx", false);
}
I think I need to somehow make button click event work on page load. But how I can make it work with relevant variables?
Sachin Singh5y ago
yes it will reset the page untill you will not specify that hey Asp.Net page cycle please don't run anything that is in my page Load if it is not a First Request , Remember every request after the first request is called a postback. so simply say asp.net that run the page load code when it is not a Postback that is on a first request only.
protected void Page_Load(object sender, EventArgs e)
{
   if (!IsPostBack)
{

        if (thisUser == null)
            lblWelcomeUser.Text = "Welcome";
        else
            lblWelcomeUser.Text = "Welcome, " + thisUser.FirstName + " " + thisUser.LastName;

        pnlCompaniesView.Visible = false;
}
}