Set an image size C#

I have a method that loads an image in my SharePoint user control.  I need to make the image stretch to fit the container.  Currently the image is too small.  I have tried this with in-line css and a style sheet.  Neither work. Is there an easy way to set the size of the image in C# to something like (width: 100%; height: 50px) ?  Here is what I have so far:

 public override void RenderControl(HtmlTextWriter writer)
        {
            imgLogo.ImageUrl = SPContext.Current.Site.Url + "/_layouts/images/Custom/PosterLogo.png";
}

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<td colspan="4">
            <asp:Image ID="imgLogo" runat="server" CssClass="posterLogo" AlternateText="Logo" />  
        </td>

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