There are two ways.
1. Define separate click events for all the link buttons as 'Rohan Leuva' suggested
2. Provide
Command Argument with link button as mentioned below :
ASPX :
<asp:LinkButton runat="server" ID="link1" OnClick="Lnk_Click" CommandArgument="1" Text="test Link 1"></asp:LinkButton>
<asp:LinkButton runat="server" ID="link2" OnClick="Lnk_Click" CommandArgument="2" Text="test Link 2"></asp:LinkButton>
<asp:LinkButton runat="server" ID="link3" OnClick="Lnk_Click" CommandArgument="3" Text="test Link 3"></asp:LinkButton>
Code Behind:
protected void Lnk_Click(object sender, EventArgs e)
{
var button = (LinkButton)sender;
var commandArgument = button.CommandArgument;
if (commandArgument == "1")
{
}
else if (commandArgument == "2")
{
}
else if (commandArgument == "3")
{
}
}