Datalist click Image

   



In code also 

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            GetData();
        }
    }


    public void GetData()
    {
        MySqlConnection con = new MySqlConnection(ConfigurationManager.ConnectionStrings["sqlcon"].ConnectionString);
        MySqlCommand cmd = new MySqlCommand("select * from tblImages", con);
        con.Open();
        MySqlDataAdapter da = new MySqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        DataList1.DataSource = ds.Tables[0].DefaultView;
        DataList1.DataBind();
        img.ImageUrl = ds.Tables[0].Rows[0][1].ToString();
    }


    protected void DataList1_ItemCommand(object source, DataListCommandEventArgs e)
    {
        if (e.CommandName == "ViewDetails")
        {
            // Response.Redirect("ViewDetails.aspx?Id=" + e.CommandArgument.ToString());
            MySqlConnection con = new MySqlConnection(ConfigurationManager.ConnectionStrings["sqlcon"].ConnectionString);
            MySqlCommand cmd = new MySqlCommand("select * from tblImages where Id='" + e.CommandArgument.ToString() + "'", con);
            con.Open();
            MySqlDataAdapter da = new MySqlDataAdapter(cmd);
            DataSet ds = new DataSet();
            da.Fill(ds);
            img.ImageUrl = ds.Tables[0].Rows[0][1].ToString();
        }
    }

As I am having MYSQL database I used Mysql rename them to Sql it you are using SQL.
Check out my video file for the working scenario