Calling Javascript function from code behind ASP.NET

Question

I\'m attempting to call a javascript method in its own file from code behind on a button click.

aspx file

protected void Next_Click(object sender, EventA         


        

Answer 1

I presume you already included the script file in your page.

If you require the postback, you need ClientScriptManager.RegisterStartupScript Method (Type, String, String, Boolean) ..

protected void Next_Click(object sender, EventArgs e)
{
    if (hidden.Value == "")
    {
        ClientScriptManager cs = Page.ClientScript;
        cs.RegisterStartupScript(this.GetType(), 'startupScript', 'drawImage();', true);
    }
}

More Info from SO

---

You can call the function from your button itself, without the postback.

and in the script

function drawImage() {
    if(document.getElementById("hidden").value != undefined || document.getElementById("hidden").value != "")
    {
        context.drawImage(video, 0, 0, 320, 240);
        var imgBase = canvas.toDataURL('image/jpeg');
        document.getElementById("hidden").value = imgBase;
        return false;
    }
}