How to call javascript function and code behind using button - javascript

How to call javascript function and code behind function using button?
<asp:button id="btnSave" onclick="btnSave();" onclientclick ="return javascriptfunction();" runat="server">
</asp:button>
I tried like this too. but no response.
<asp:button id="btnSave" onclick="btnSave();" onclientclick ="return true;" runat="server">
</asp:button>
even, javascript function return true, its not calling codebehind function. May i know reason?

The code should be something like this -
JavaScript:
<script>
function save()
{
return confirm('Are you sure you want to continue?');
}
</script>
ASPX:
<asp:Button ID="btnSave" OnClick="btnSave_Click" OnClientClick="return save();"
runat="server" />
C# CodeBehind:
protected void btnSave_Click(object sender, EventArgs e)
{
// Do something
}
It basically call JavaScript function before posting back to server. Whether post back to server or not is depending upon the return value from JavaScript function.
Button control's OnClick is an server side event so you need to attach to server side click event.

The best way I have found to do this is from code behind using RegisterStartupScript
ScriptManager.RegisterStartupScript(this, this.GetType(), "name", "javascriptfunction();", true);

Related

Trigger c# Event from JavaScript Function

I'm trying to call c# event from javascript function. I tried this:
<script type="text/javascript">
function LikeClick() {
document.getElementById('<%=Helper.ClientID %>').click();
}
</script>
<asp:Button ID="Helper" runat="server" OnClick="Helper_Click" />
But it doesn't trigger the c# event.
I believe a <asp:Button> will natively post the form back without a client side event handler. You need a control that does not natively post back but instead uses a client side click handler to call the __doPostBack() function.
Change
<asp:Button ID="Helper" runat="server" OnClick="Helper_Click" />
to this
<asp:LinkButton ID="Helper" runat="server" OnClick="Helper_Click" />

How to run javascript using server side code in ASP.Net Web Form application in update panel?

I want to use some javascript code inside update panel in ASP.Net web form application using serverside code. The problem is the following code only works if i used it outside update panel but not works inside, even with alert.
<form id="form1" runat="server">
<div>
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Button ID="Button1" runat="server" Text="Server" OnClick="Button1_Click"/><br />
<asp:Button ID="Button2" runat="server" Text="Cleint" OnClientClick="alert('Hello World(Cleint)')"/>
</ContentTemplate>
</asp:UpdatePanel>
</div>
</form>
Code Behind
protected void Button1_Click(object sender, EventArgs e)
{
this.ClientScript.RegisterStartupScript(this.GetType(),
"ShowMessage", string.Format("<script type='text/javascript'>alert('{0}')</script>",
"Hello World (Server)"));
}
when running this application only the Client Click event works but not the server side event. However when removing update panel ant try again both events work.
I searched a lot and found some similar questions but all answers didn't work. I just wanna to fix problem for the example i put above. Thanks
Try to replace your code behind in the button click event with this:
ScriptManager.RegisterStartupScript(this, this.GetType(), this.ClientID, string.Format("alert('{0}')", "Server"), true);
Hope this helps.

ASP.Net get ScriptManager.RegisterClientScriptBlock return on UpdatePanel hiddenField

I am trying to obtain the return of a Javascript function that I call ont server side using ScriptManager.RegisterClientScriptBlock .
Currently, my javascript function save the value in a HiddenField that is contained in an UpdatePanel. When I call the method , I run the ScriptManager.RegisterClientScriptBlock and after that get the value of the HiddenField , but always returns me the value of the previous call. Here I show the code:
My User Control ASPX Side:
<script>
var num = 0;
function getReturn() {
num = num + 1;
var hr= document.getElementById('<%= hdf.ClientID %>');
hRetorno.value = num;
}
</script>
...
<asp:UpdatePanel ID="up1" UpdateMode="Conditional" runat="server">
<ContentTemplate>
<asp:HiddenField ID="hdf" runat="server" />
</ContentTemplate>
</asp:UpdatePanel>
My User Control Server Side Code:
public String GetReturn()
{
return MyControl.jsGetReturn(this.Page, this.hdf);
}
private static String jsGetReturn(Page page, HiddenField hid)
{
ScriptManager.RegisterStartupScript(page, page.GetType(), "key", "getReturn();", true);
return hid.Value;
}
Index Page ASPX Side:
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<div style="width:720px; height:480px;">
<uc1:MyControl runat="server" id="MyControl1"/>
</div>
<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<asp:Button ID="btn" runat="server" OnClick="btn_Click" />
<asp:TextBox ID="txt" runat="server" ></asp:TextBox>
</ContentTemplate>
</asp:UpdatePanel>
Index Page Server Side Code:
protected void btn_Click(object sender, EventArgs e)
{
txt.Text = MyControl1.GetReturn();
}
You can not do these things simultaneously.
Set value of hidden field from server side code using javascript via RegisterClientScriptBlock or RegisterStartupScript.
And retrieve that hidden filed value in server side code at the same time.
This is because, (changed) hidden field value is available to server-side code only when there is postback, when you set the value from server-side, there is no postback happening, that is why you are always getting previous value , i.e. that old value which is posted back to page.
EDIT
When you invoke RegisterClientScriptBlock or RegisterStartupScript, it won't make JS call instantly, rather it just append a javascript call before or after <form.. tag based on what you used and they are called on document load, so that means in jsGetReturn when you call RegisterStartupScript, it will set value of hidden field in document load, - hid.Value will not have updated value, as it is yet to be incremented via document load.

ASP.Net session not updated in javascript

when my button is clicked I fire the javascript to get the session..
But value of session not updated...
alert('<%= Session["file"]%>');
It won't be up to date if its changed after the page is rendered.
You might want to look at page methods (an ajax system) or another ajax approach.
Any inline code once rendered to the page will not change, which is a normal behavior.
use a Hidden field instead.
mark-up:
<asp:HiddenField ID="HiddenField1" runat="server" />
<asp:Button ID="Button1" runat="server" Text="Button" onclick="Button1_Click" />
code-behind:
protected void Button1_Click(object sender, EventArgs e)
{
Session["file"] = "Data Here";
HiddenField1.Value = Session["file"].ToString();
}
javascript:
alert(document.getElementById('<%= HiddenField1.ClientID %>').value);

click() Event in javascript with a PARAM?

I'm using the event click() to call a method in Code Behind, like this:
HTML
<asp:button bordercolor="White" id="btnAddGS" onclick="AddGSBandeira" runat="server">
JAVASCRIPT
$("#ctl00_ContentPlaceHolder1_btnAddGS").click();
C#
public void AddGSBandeira(object sender, EventArgs e)
{
}
Its work normally, but I need to pass a param in the javascript call, like this:
$("#ctl00_ContentPlaceHolder1_btnAddGS").click("param");
But I do not know how this works ...can anybody help?
The best thing to do is create a hidden control and populate it's value with JavasScript on the click event. Your code behind will be able to access that value on your postback (AJAX or otherwise).
Markup
<asp:HiddenField ID="myHiddenField" runat="server" />
<asp:button bordercolor="White" id="btnAddGS"
onclick="AddGSBandeira"
onclientclick="SetHiddenValue()" runat="server">
JavaScript
function SetHiddenValue()
{
document.getElementById("<%=myHiddenField.ClientID%>").value = "[Your value here]";
}
C#
public void AddGSBandeira(object sender, EventArgs e){}
{
var jsVal = myHiddenField.Value;
}
You can do this with trigger.
http://api.jquery.com/trigger/
$("#ctl00_ContentPlaceHolder1_btnAddGS").trigger("click",["param"]);
I believe the 2nd parameter to trigger should be an array of arguments to pass to the function.

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