in bulleted list selected item show image,price according to selected category..

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C#

ASP.NET

here i attach a code for if i'm selecting one category from bulleted list it will show image,price,name for items in particular category....
i try following code it shows error...
can anyone solve it and it entirly wrong means pls giv me correct coding for that.

Error Code:

protected void BulletedList1_Click(object sender, BulletedListEventArgs e)
    {
        categ(cat_name);
    }
    public void categ(string cat_name)
    {
        if (con.State == ConnectionState.Closed)
        {
            con.Open();
        }
        SqlCommand cmd = new SqlCommand("select pro_img,pro_name,price from product where pro_category='books'", con);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        BulletedList1.DataSource = ds;
        BulletedList1.DataBind();
        con.Close();
    }