populate gridview on dropdownlist indexchanged

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

private void BindData()
   {
       if (ddlTguidedit.SelectedIndex==0)
       {
           string strQuery = "SELECT [Pdfid],[Arpdf_name],[Arpdf_des],[pdf_date] FROM [books_alaa].[dbo].[Tbl_uploadpdf]";
           SqlCommand cmd = new SqlCommand(strQuery);
           GridView1.DataSource = GetData(cmd);
           GridView1.DataBind();
       }
       else
       {
           string strQuery = " SELECT Pdfid, Enpdf_name AS Arpdf_name, Enpdf_des AS Arpdf_des, pdf_url, pdf_date FROM Tbl_uploadpdf";
           SqlCommand cmd = new SqlCommand(strQuery);
           GridView1.DataSource = GetData(cmd);
           GridView1.DataBind();
       }
   }

   private DataTable GetData(SqlCommand cmd)
   {
       DataTable dt = new DataTable();
       SqlConnection con = new SqlConnection(strConnString);
       SqlDataAdapter sda = new SqlDataAdapter();
       cmd.CommandType = CommandType.Text;
       cmd.Connection = con;
       con.Open();
       sda.SelectCommand = cmd;
       sda.Fill(dt);
       return dt;
   }

protected void ddlTguidedit_SelectedIndexChanged(object sender, EventArgs e)
   {
       if (ddlTguidedit.SelectedIndex == 0)
       {
           string strQuery = "SELECT [Pdfid],[Arpdf_name],[Arpdf_des],[pdf_date] FROM [books_alaa].[dbo].[Tbl_uploadpdf]";
           SqlCommand cmd = new SqlCommand(strQuery);
           GridView1.DataSource = GetData(cmd);
           GridView1.DataBind();
       }
       else
       {
           string strQuery = " SELECT Pdfid, Enpdf_name AS Arpdf_name, Enpdf_des AS Arpdf_des, pdf_url, pdf_date FROM Tbl_uploadpdf";
           SqlCommand cmd = new SqlCommand(strQuery);
           GridView1.DataSource = GetData(cmd);
           GridView1.DataBind();
       }
   }