How to display in a form the next object of a collection?

[espaces70]

I have a list of objects produced.
after click on next I want to display the next product in the form

in my asp page I have the following form:

<form id="formNF" runat="server">
    
    <asp:TextBox ID="txtRef" runat="server"></asp:TextBox>
    <asp:TextBox ID="txtArticle" runat="server"></asp:TextBox>
    <asp:TextBox ID="txtQauntity" runat="server"></asp:TextBox>
    
    
    <asp:Button ID="ButtonNext" runat="server" Text="Next product" OnClick="ButtonNext_Click"/>
    </form>

In my code-behind:

 private int i; 
    protected void ButtonNext_Click(object sender, EventArgs e) { 
         int nbrproducts = command.getListeproducts().Count; 
         i++; 
         for(i=0;i<nbrproducts;) { 
           mdeTxtRef.Text = command.getListeproducts()[i].Ref; 
           mdeTxtQte.Text = command.getListeproducts()[i].Qte; 
         } 
    }

But it seems as ASP doesn't like this. Have u got an idea? thk u.

[Frinavale]

Store "i" into Session, or ViewState, or ControlState so that the page can retrieve what the last index was that the user was viewing.

For example:

private int i;

protected void Page_Load(object sender, EventArgs e){
  if(IsPostBack == true){
    i = (int)ViewState["productIndex"];
  }else{
    i = 0;
  }
}

void Page_PreRender(object sender, EventArgs e){
  ViewState["productIndex"] = i;
}

protected void ButtonNext_Click(object sender, EventArgs e) { 
  int nbrproducts = command.getListeproducts().Count; 
  i++; 
  //not sure why you're looping at this point...
  //you know the index..just retrieve the item.
  //for(i=0;i<nbrproducts;) { 

  if(i<getListeproducts.Length()){
    //not sure what command is either....
    mdeTxtRef.Text = command.getListeproducts()[i].Ref; 
    mdeTxtQte.Text = command.getListeproducts()[i].Qte; 
  }
  //} 
}

[espaces70]

Thank you for this answer, I stored "i" in textbox.
but your solution seem better, I will try with viewstate.
thanks.