Font awesome inside asp button

You can use a LinkButton

<asp:LinkButton runat="server" ID="btnRun" Text="<i class='icon-camera-retro'></i> Search" 
                ValidationGroup="edt" OnClick="btnRun_Click" CssClass="greenButton" />

They do support html in the text field.

Use LinkButton

<asp:LinkButton runat="server" ID="btnRun" ValidationGroup="edt" OnClick="btnRun_Click" CssClass="greenButton" > <i class='icon-camera-retro'></i> Search </asp:LinkButton>

You can't with the default asp.net button you will need to use a HTML button and give it runat=server attribute:

<button runat="server" id="btnRun" class="btn btn-mini" title="Search">
    <i class="icon-camera-retro"></i> Search
</button>

So use code behind with this you add:

onserverclick="functionName" 

To the button, then in your C# do:

protected void functionName(object sender, EventArgs e)
{
    Response.Write("Hello World!!!");
}

So final button looks like:

<button runat="server" id="btnRun" onserverclick="functionName" class="btn btn-mini" title="Search">
    <i class="icon-camera-retro"></i> Search
</button>

You can do it, jut not purely with CSS. You just need to set the Text property on the button to the unicode value of the fontawesome character and give the button the 'fa' css class so it takes up the fontawesome font.

<asp:Button ID="Button1" runat="server" 
    Text="\xF135" CssClass="fa" />

I made this helper library that provides all the icon codes strongly-typed if that turns your crank:

<asp:Button ID="Button1" runat="server" 
    Text="<%# FontAwesome.Icons.Rocket %>" CssClass="fa" />

Nuget: Install-Package FontAwesome-ASP.NET

Source: https://github.com/kemmis/FontAwesome-ASP.NET