Question

I get the error message

The format of the input string is incorrect.

 public partial class Fiche_Ordre : DevExpress.XtraEditors.XtraForm
    {
        public string ClientID = "", OderId = "", TempId = "";
       .....

        public Fiche_Ordre()
        {
            InitializeComponent();

            Constuct_Page();

        }

        public Fiche_Ordre(string OrderID)
        {
            InitializeComponent();
            Constuct_Page();

            Pers_Ordre oPersOrdr = oOrder_BL.Get_OrdreOne_BL(ClientID, Convert.ToInt32(OderId), false);
            textEdit_RaisonSoc.Text = oPersOrdr.RaisonSoc;
        }

when I call the constuctor from other form:

 private void GoToFiche(object sender, EventArgs e)
        {
            try
            {                              
                Fiche_Ordre f_Fiche = new Fiche_Ordre("1");
               // Fiche_Ordre f_Fiche = new Fiche_Ordre(gridView_Liste_Ordres.GetRowCellValue(0, "NO_ORDRE").ToString());
                f_Fiche.Show();
            }
            catch (Exception excThrown)
            {
                MessageBox.Show(excThrown.Message);          
            }

I have constructor: public Fiche_Ordre(string OrderID)

Answer 1

 public Fiche_Ordre(string OrderID)
        {
            InitializeComponent();
            Constuct_Page();

            Pers_Ordre oPersOrdr = oOrder_BL.Get_OrdreOne_BL(ClientID, Convert.ToInt32(OderId), false);
            textEdit_RaisonSoc.Text = oPersOrdr.RaisonSoc;
        }

You are passing OrderID and using OderId.

Watch your case and spelling.