Here is my button
<asp:Button ID="myButton" Text="Click Me" OnClick="doSomething(10)" runat="server" />
Here is the server function
public void doSomething(int num)
{
int someOtherNum = 10 + num;
}
When I try to compile the code I get the error "Method Name Expected" for the line:
<asp:Button ID="myButton" Text="Click Me" OnClick="doSomething(10)" runat="server" />
What am I doing wrong? Am I not allowed to pass values to the server from an OnClick event?
There are two problems here. First, the onclick event has a specific signature. It is
MethodName(object sender, EventArgs e);
Second, in the markup, you need to pass the Method name only with no parentheses or params.
<asp:Button ID="myButton" Text="Click Me" OnClick="doSomething" runat="server" />
Then change your codebehind as follows:
public void doSomething(object sender, EventArgs e)
{
....
}
The passing of parameters can done on a client side click event handler, in this case OnClientClick, but not on the server side handler.
There is simpler solution. You could use ASP button OnCommand event.
More about here: http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.button.oncommand.aspx
OnClick of the Button is an Event Handler. To hook a function to an eventHandler you need to obey the Contract that was defined by the EventHandler, as mentioned by Jose. OnClick is bound to a function of the format void doSomething(object sender, EventArgs e). So your function should be of the same format.
I am unsure why would want to pass a parameter to the Event Handler. If you want to take some manuplation you need to do that using some other control.
<asp:TextBox ID="txtNumber" runat="server" /><asp:Button ID="myButton" Text="Click Me" OnClick="doSomething" runat="server" />
And in the Code
public void doSomething(object sender, EventArgs e)
{
int AnotherNumber= Int32.Parse(txtNumber.Text)+10;
}
You Must Change your Method's Structure to be like
public void doSomething(object sender, EventArgs e)
{
....
}
and for passing parameters you need a work around like this :
for example if you in an Html control you may but your parameter in an attribute value (such as ID in this exapmle) and then retrieve it in the server side handler
i.e to make an control changing the style color
Html :
<a href="" id="Grey" runat="server" onserverclick='ApplyStyleEvent'></a>
Code :
protected void ApplyStyleEvent(object sender, EventArgs e)
{
Profile["SelectedStyle"] = ((HtmlControl)sender).ID;
Response.Redirect("");
}
and so on.
Related
1st Page.
<asp:Button ID="Button1" runat="server" Text="Submit" CssClass="btn btn-primary" OnClick="Button1_Click" OnClientClick="return" />
Actually, I need to call this page from another 2nd.aspx.cs page.
public void Page_Load(object sender, EventArgs e){
//Do some stuff in the page load event handler.
}
public void Button1_Click(object sender, EventArgs e){
//Do some stuff in the button click event handler.
}
I change the button Access Modifiers property to public from the designer page.
public global::System.Web.UI.WebControls.Button Button1;
2nd Page
Create an Object in this page to access 1st page.
FirstPageName firstPage = new FirstPageName();
firstPage.Button1_Click();
This doesn't work!
1st Page.
FirstPageName.aspx page.
<asp:Button ID="Button1" runat="server" Text="Submit" CssClass="btn btn-primary" OnClick="Button1_Click" OnClientClick="return" />
FirstPageName.aspx.cs page.
public void Button1_Click(object sender, EventArgs e){
//Do some stuff in the button click event handler.
}
Change the button Access Modifiers property to public from the designer page.
public global::System.Web.UI.WebControls.Button Button1;
2nd Page
Here, we can use 2 methods.
1st Method
Create an Object in this page to access 1st page.
FirstPageName firstPage = new FirstPageName();
firstPage.Button1_Click(firstPage.Button1, EventArgs.Empty);
2nd Method
Create an Object in this page to access 1st page.
FirstPageName firstPage = new FirstPageName();
firstPage.Button1.Click += new EventHandler(firstPage.Button1_Click);
I'm also attaching another two methods. Try this, This works for me.
YourButton.RaiseEvent(new RoutedEventArgs(Button.ClickEvent));
Button.PerformClick();
I have an button in my aspx web page, which should be 'clicked' in my code behind c# code. The OnClientClick method then call a JS confirm dialog box and so the btn_Click function only get executed when user click 'OK'...
This is my code so far:
Variante 1
aspx:
<asp:Button runat="server" ID="btnConfirm" Text="Confirm" OnClick="btnConfirm_Click" />
aspx.cs:
protected void Page_Load(object sender, EventArgs e)
{
// set OnClientClick
btnConfirm.OnClientClick = "confirm('Save in DB?');";
// invoke method
Type t = typeof(System.Web.UI.WebControls.Button);
object[] p = new object[1];
p[0] = EventArgs.Empty;
MethodInfo m = t.GetMethod("OnClick", BindingFlags.NonPublic | BindingFlags.Instance);
m.Invoke(btnConfirm, p);
}
protected void btnConfirm_Click(object sender, EventArgs e)
{
//save something in database
}
Got code samples by: http://forums.asp.net/t/1046550.aspx?How+do+you+raise+a+button+click+event+from+outside+the+button+
I want to call the OnClientClick method, but when I replace 'OnClick' with 'OnClientClick' this error appear:
System.NullReferenceException was unhandled by user code
Message=Object reference not set to an instance of an object.
Edit:
Variante 2:
I tried to rewrite my program like this:
aspx:
<script language="javascript">
function invokeButtonClick() {
document.getElementById("btnConfirm").click();
}
function Validate() {
return confirm('Save in db?');
}
</script>
<asp:Button runat="server" ID="btnConfirm" Text="Confirm" OnClick="btnConfirm_Click" OnClientClick="return Validate();" />
aspx:cs:
protected void Page_Load(object sender, EventArgs e)
{
ScriptManager.RegisterStartupScript(this, GetType(), "InvokeButton", "invokeButtonClick();", true);
}
protected void btnConfirm_Click(object sender, EventArgs e)
{
// save something in database
}
But then the page postback before my btnConfirm_Click function get called...
Thanks,
Michael
If OnClientClick has a return value of true then the codebehind OnClick event will fire. If OnClientClick is returned false then it won't.
If OnClientClick doesn't return anything the codebehind event will fire regardless. So you want..
<asp:Button runat="server" ID="btnConfirm" Text="Confirm" OnClick="btnConfirm_Click" />
<script language="javascript">
function Validate() {
return confirm('Save in db?');
}
</script>
Codebehind:
protected void Page_Load(object sender, EventArgs e)
{
// set OnClientClick
btnConfirm.OnClientClick = "return Validate();";
}
protected void btnConfirm_Click(object sender, EventArgs e)
{
//save something in database
}
UPDATE:
This post just came to my attention, don't know why I didn't include it in my original post but you can use 'OnClientClick' in the aspx tag:
<asp:Button runat="server" ID="btnConfirm" OnClientClick="return Validate();" Text="Confirm" OnClick="btnConfirm_Click" />
<script language="javascript">
function Validate() {
return confirm('Save in db?');
}
</script>
You need to Add both the events on the button click. OnClientClick handles the Client side script code and OnClick handles the server side event calling.
So add both events and there handlers. The NullReferenceException you are getting because of that.
<asp:Button runat="server" ID="btnConfirm" Text="Confirm" OnClick="btnConfirm_Click" OnClientClick="return Validate();" />
and in your javascript code can be
function Validate(){
if (valied())
return true;
return false;
}
100% code behind confirmation! Sometiems its so annyoing to Code behind or Server side confirmation in asp.net when you want to Delete or Update something, I got its solution after a long search as below:
<asp:Button ID="btnSave" runat="server" Text="Save" OnClientClick="return confirm('Are you sure to BLOCK this customer ?')" OnClick="btnSave_Click" />
Now whenever you will click this button it 'll ask to confirm, if you 'll select "NO" page will not post and if you select "Yes" then page will post and your button click event will be fire... like below
Code behind:
protected void Page_Load(object sender, EventArgs e)
{
}
// Before coming here,,,there will be confirmation
protected void btnSave_Click(object sender, EventArgs e)
{
GetCustomerInfo();
}
In my .aspx page I have a 'input' html tag, also an asp button.
<input id="Name" type="text" runat="server" clientidmode="Static" />
<asp:Button Width="100" type="submit" ID="sendOrder" runat="server" OnClick="SubmitForm" Text="Submit" />
On page load, I am filling the value in input tag from code behind, like this:
Name.Value= "X";
But now if I change value of this text box from browser, lets say "Y", and click on Submit button, then I get the old value, but not the new one.
protected void SubmitForm(object sender, EventArgs e)
{
var test= Name.Value; // here I get old value
}
How can I get the altered value?
Make sure you are only setting the value to "X" when its not a postback:
if (!Page.IsPostBack){
Name.Value= "X";
}
Otherwise when clicking the submit button, the Page_Load() event will change the value from "Y" back to "X".
You need to use !IsPostBack on Page_Load shown as below:
protected void Page_Load(object sender, EventArgs e)
{
//it's important to use this, otherwise textbox old value overrides again
if (!IsPostBack)
{
Name.Value= "X";
}
}
Suggestion:
We can use use <input></input> control in asp.net but best practice is to use <asp:TextBox></asp:TextBox> control instead.
Here is the sample example:
HTML
<asp:TextBox ID="Name" runat="server"></asp:TextBox>
<asp:Button Width="100" ID="sendOrder" runat="server" OnClick="SubmitForm"
Text="Submit" />
Code-behind:
protected void Page_Load(object sender, EventArgs e)
{
//it's important to use this, otherwise textbox old value overrides again
if (!IsPostBack)
{
Name.Text = "Some Value";
}
}
protected void SubmitForm(object sender, EventArgs e)
{
var test = Name.Text; //now get new value here..
}
Check for IsPostback in Page_Load so you don't overwrite the values that are submitted!
You don't need all the else portion, just do this
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
//code to execute here only when an action is taken by the user
//and not affected by PostBack
}
//these codes should be affected by PostBack
}
So I basically have two textboxes in the aspx file which get populated by dates (using the jquery datepicker) as given below
Start Date: <asp:TextBox ID="TxtDatepicker_start" runat="server" Width = 125px >
</asp:TextBox>
End Date: <asp:TextBox ID="TxtDatepicker_end" runat="server" Width = 125px >
</asp:TextBox>
<asp:Button ID="Button_daterecords" runat="server" Text="Show records" OnClick ="SQLDisplay_Date_records" /><br />
However when I try to determine what has been stored in the text boxes for further processing in the code behind using this function
protected void SQLDisplay_Date_records()
{
string date1 = TxtDatepicker_end.Text;
string date2 = TxtDatepicker_end.Text;
}
I am getting this error
No overload for 'SQLDisplay_Date_records' matches delegate 'System.EventHandler'
Can someone explain this to me ,I apologize for the naive question but I am still making my way around with ASP.NET and C#
Wild guess, OnClick is a event. which has a object (source) and eventargs.
Try setting it to
Protected void SQLDisplay_Date_records(object sender, EventArgs e)
{
string date 1 = TxtDatepicker_end.Text;
string date 2 = TxtDatepicker_end.Text;
}
Your method signature is incorrect.
The protected void SQLDisplay_Date_records()
should be protected void SQLDisplay_Date_records(object sender, EventArgs e)
As it is an OnClick Event and it should take an Event Argument as a parameter.
this seemed simple at first but I can't get it to work.
I have the following scenario:
<asp:ListView ID="CommentsListView" runat="server">
<LayoutTemplate>
<asp:PlaceHolder ID="itemPlaceholder" runat="server" />
</LayoutTemplate>
<ItemTemplate>
<UC:Comment runat="server" CommentItem="<%# CurrentComment %>" />
<br />
</ItemTemplate>
</asp:ListView>
<asp:TextBox ID="NewComment" runat="server" />
<asp:ImageButton ImageUrl="/images/ball.png" runat="server"
OnClick="SubmitComment" />
Code:
protected void Page_Load(object sender, EventArgs e)
{
RenderListView();
}
protected void RenderListView()
{
CommentsListView.DataSource = //Get the data source objects
CommentsListView.DataBind();
}
protected CommentObject CurrentComment
{
get { return (CommentObject)Page.GetDataItem(); }
}
protected void SubmitComment(object sender, ImageClickEventArgs e)
{
//code to submit comment
RenderListView();
}
basically, when I submit a comment, I want to see it in the ListView, but I don't. "MyControl" gets a null comment in the post-back, for all of the items (not just the new one).
Only after I refresh the page, I can see the new comment that I'v submitted. I can't however refresh the page every submit because this code is inside an UpdatePanel (the issue occurs without the UpdatePanel as well).
Any idea how to solve this?
I can't find any specifics on this, but I have a hunch the user control in your ItemTemplate is causing the issue. Can you remove it and see if it works?
I notice that you are calling RenderListView in both SubmitComment and PageLoad which I believe will cause it to fire twice when the button is clicked (with PageLoad firing first). It looks like the code you posted is simplified. Is it possible that there is something happening in the PageLoad which is sabotaging your SubmitComment steps?
I finally solved it, if anyone else may encounter this -
The solution was to avoid "<%#" and instead use the ItemDataBound event:
<asp:ListView ID="Comments" runat="server"
OnItemDataBound="CommentsItemDataBound">
and the method itself:
protected void CommentsItemDataBound(object sender, ListViewItemEventArgs e)
{
var commentItem = (Comment)(((ListViewDataItem)e.Item).DataItem);
var commentControl = (Comment)e.Item.FindControl("CommentControl");
commentControl.CommentItem = commentItem;
}
This way, the binding of each control works as expected.