Develop Reference

Why XAML button can't invoke argumentless function

I have function in create.cs
private void FillGrid()
{
ClearingEntities CE = new ClearingEntities();
var Accountss = CE.Accounts;
DataGrid1.ItemsSource = Accountss.ToList();
}
I invoke this function from other .cs files just writing FillGrid(); without any arguments
but from xaml in button Click="FillGrid" gives error
click auto generated functions have
private void Button_Click(object sender, RoutedEventArgs e)
I don't want insert those object sender, RoutedEventArgs e arguments
if I insert those to my function's arguments then other calling should be changed
to
FillGrid([argument],[argument]);
note: it is not event handling function just fill data stuff
how to call FillGrid() from xaml? without changing create.cs

This is just the way Button Event's work.
Read more about EventHandler here
Why don't you just use this:
<Button Click="FillGridClicked" />
//sender = button, RoutedEventArgs = arguments of that event
private void FillGridClicked(object sender, RoutedEventArgs e)
{
FillGrid();
}
Every ClickEventHandler needs these arguments as it is a custom delegate defined that way. If you really want to emit this you need to extend the button and create a custom click handler for yourself. (see this for example)

ASP.NET: add postback to anchor

In my javascript file, I got an ajax to get all list and iterate these data and append <a id='userID' class='btn'>Assign ID<> to my list.
So, how do a add postback to these anchor and redirect it inside my method in the server. Below is my code but didn't work. When I click the achor button, it just redirect/refresh to the same page without doing any changes and didn't show the text.
<a id='uniqueID' class='btn assignID' href='javascript:void(0);' onclick='javascript:__doPostBack('uniqueID','')'>Assign ID</a>
protected void Action_assignID(object sender, EventArgs e)
{
// assign ID action
Response.Write("Pass");
}

You should be changed your button to:
<a id='uniqueID' class='btn assignID' href='javascript:void(0);' onclick="javascript:__doPostBack('uniqueID','Assign ID')">Assign ID</a>
And it's a good idea to implement the IPostBackEventHandler interface in your codebehind as below:
public partial class WebForm : Page, IPostBackEventHandler
{
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack)
{
}
}
public void RaisePostBackEvent(string eventArgument)
{
// do somethings at here
}
}
Hope this help!

The __doPostBack method really doesn't do anything special except, well... perform a POST operation back to the same page with two specific form arguments.
The first parameter is the __EVENTTARGET and the second parameter is the __EVENTARGUMENT.
The magic all happens in ASP.Net where it automagically wires up your controls to event handlers, but since you are creating these entirely in JavaScript the server doesn't know that those controls exist.
However, you can manually grab these values and do something with them.
//Client Side JavaScript:
__doPostBack('my-event', '42');
//Code Behind
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack)
{
var target = Request.Params["__EVENTTARGET"];
var args = Request.Params["__EVENTARGUMENT"];
Target.Text = target; // 'my-event'
Argument.Text = args; // '42'
}
}

Is there a better way to close buttons on click?

I'm a beginner and have an assignment in which I must program the game of NIM. I begin with 15 "tokens" and at each turn a maximum of three can be removed, or "hidden". So far I am hiding these tokens on click by doing the following.
private void button1_Click(object sender, EventArgs e)
{
button1.Visible = false;
}
private void button2_Click(object sender, EventArgs e)
{
button2.Visible = false;
}
I simply copied and pasted that multiple times and changed the button numbers so that my buttons will close on click. This might be obvious, but is there a more efficient way to do this, instead of having 15 button close methods?

You can use the same click event for every single button, and make use of the sender object, casting it to Button:
private void buttonsToClose_Click(object sender, EventArgs e)
{
((Button)sender).Visible = false;
}
Then just add that handler to every single button you want to close itself on click.
Note, though, that this will throw an InvalidCastException if you or anyone else uses this handler on an object that is not a Button, so if you're actually going to use this code I would add some sort of conditional to check the real type of the sender.
Additionally, you could reuse this for any Control object by casting sender to Control instead, given that Button inherits from Control, and all Control objects have the Visible property. Here's an example, with a conditional to guard against an invalid cast:
private void controlToMakeInvisible_Click(object sender, EventArgs e)
{
if (sender.GetType() == typeof(Control))
{
((Control)sender).Visible = false;
}
}
A final note - it seems from your post like you may have a slight misunderstanding about the way events are created and wired in with objects in Windows Forms. If you go into the Designer, add a click event, and see it pop into your Form code as follows:
private void button1_Click(object sender, EventArgs e)
the name of this method has no bearing on its function. The button1 part of button1_Click doesn't actually have any logical linkage with the Button button1 - it's just the default name assigned by the Designer. The actual assignment of the method button1_Click to the Button.Click event is auto-generated into your Form's Designer.cs method.
The point of this is that if you copy and paste button1_Click and change every incidence of button1 with button2, like so:
private void button2_Click(object sender, EventArgs e)
{
button2.Visible = false;
}
it's not going to fire when button2 gets clicked. In actual fact, it's never going to fire at all, because the method hasn't actually been connected to any controls/events.

just call your event in a foreach loop.
private void Form1_Load(object sender, EventArgs e)
{
foreach (var button in Controls.OfType<Button>())
{
button.Click += button_Click;
}
}
void button_Click(object sender, EventArgs e)
{
((Control) sender).Visible = false;
}
if you change:
Controls.OfType<Button>()
to
Controls.OfType<Control>()
it will set visible to false for any Control. so you can control what item you want the event to be raised for easily.
OfType summary: Filters the elements of an IEnumerable based on a specified type.

From UserControl page, Call Page_Prerender in Parent page

I have a aspx page name MakeRedemption.aspx, in which have a UserControl (Search.ascx).
There is Page_Prerender() in the MakeRedemption.aspx.
I would like to ask, how can I call the Page_Prerender() from MakeRedemption.aspx, by a function in Search.ascx.
It is something as follow :
Actually there is a looping in one of the function in my User Control page.
The Page_Prerender (MakeRedemption.aspx) will trigger after all the loop finish.
What I want is :
Everytime before end of each itme of the loop, I will like to trigger the Page_Prerender on the MakeRedemption.aspx to do something.
Something like :
for (int i = 0 ; i < 10 ; i ++)
{
//some code here
// I would like to trigger Page_Prerender here to do something before end of the loop.
} // the Page_Prerender (in MakeRedemption.aspx) trigger after all the loop finish.
Means that, this for loop has i = 10, thus, I would like to trigger the Page_Prerender 10 times inside the for loop.
My PreRender function in the aspx file is as follow :
protected void Page_Prerender(object sender, EventArgs e)
{
//some code here
}
Not sure this Page_Prerender() is consider as the auto generate OnPreRender() or not.
I would like to trigger this Page_Prerender() instead of OnPreRender() .
Sorry if I am asking a stupid question, I am new in programming and c#.
Kindly advise.
Thanks.

Finally i find the way to do it, the oodng is as follow :
Add this following code in the aspx.cs page:
delegate void DelMethodWithoutParam();
protected void Page_Load(object sender, EventArgs e)
{
DelMethodWithoutParam delParam = new DelMethodWithoutParam(Page_prerender);
this.ucSearchGifts.PageMethodWithNoParamRef = delParam;
}
Page_prerender(){
//some code here...
}
and add this following code in the user control cs page:
private System.Delegate _delNoParam;
public Delegate PageMethodWithNoParamRef
{
set { _delNoParam = value; }
}
protected void Button1_Click(object sender, EventArgs e)
{
_delNoParam.DynamicInvoke();
}
When click on the Button1 in user control page, the Page_prerender() in aspx page, which is parent page, will be trigger.

Run the button event handler before page_load

I have a table with all the objects I have in my db. I load them in my Page_Load function. I have a text field and a button that when clicking the button, I want the handler of that click to put a new object with the name written in the text field in the db.
Now, I want that what happens after the click is that the page loads again with the new item in the table. The problem is that the button event handler is run after the Page_Load function.
A solution to this would be to use IsPostBack in the Page_Load or use the pre load function. A problem is that if I would have 3 different buttons, I would have to differ between them there instead of having 3 different convenient functions.
Any solutions that don't have this problem?
Code:
protected void Page_Load(object sender, EventArgs e)
{
if (Session["userId"] == null)
Response.Redirect("Login.aspx");
// LOAD DATA FROM DB
}
protected void CreateObject(object sender, EventArgs e)
{
// SAVE THE NEW OBJECT
}

Maybe you should try loading your data during PreRender instead of Load
protected void Page_Load(object sender, EventArgs e)
{
this.PreRender += Page_PreRender
if (Session["userId"] == null)
Response.Redirect("Login.aspx");
}
protected bool reloadNeeded {get; set;}
protected void CreateObject(object sender, EventArgs e)
{
// SAVE THE NEW OBJECT
reloadNeeded = true;
}
protected void Page_PreRender(object sender, EventArgs e)
{
if(reloadNeeded || !IsPostBack)
// LOAD DATA FROM DB
}

You can check the event target and do what you need then:
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack)
{
string eventTarget = Page.Request.Params["__EVENTTARGET"];
if(whatever)
{
//do your logic here
}
}
}
Get control name in Page_Load event which make the post back

Use the Page_PreRenderComplete event to retrieve your table. That way your page will always have the most recent data available after all user events have fired.

Why don't you move what you have in the click event into a new method. Then call that method as the first line in your page load?

An old question but I faced the same problem in my C#/ASP.NET Website with master/content pages: a click on a link on the master page should change a query parameter for a gridview on the content page. As you stated the button click event is handled after Page_Load. But it is handled before Page_LoadComplete (see the information about ASP.NET Page Life Cycle), so you can change the page content there.
In my case I solved the problem by setting a session variable in the click event in the master page, getting this variable in the Page_LoadComplete event in the content page and doing databind based on that.
Master page:
<asp:LinkButton ID="Btn1" runat="server" OnCommand="LinkCommand" CommandArgument="1" >Action 1</asp:LinkButton>
<asp:LinkButton ID="Btn2" runat="server" OnCommand="LinkCommand" CommandArgument="2" >Action 2</asp:LinkButton>
protected void LinkCommand(object sender, CommandEventArgs e)
{
HttpContext.Current.Session["BindInfo", e.CommandArgument.ToString());
}
Content page:
protected void Page_LoadComplete(object sender, EventArgs e)
{
string BindInfo = HttpContext.Current.Session["BindInfo"].ToString();
YourBindDataFunction(BindInfo);
}