How to save variables per user session per page

Question

I am using three webparts. Webpart A creates a value when the user clicks on the button in Webpart A. WebPart B uses this value to create a list with items the user can select. WebPart C uses both values to create a string for testing purposes.

WebPart B uses this list to fill a dropdownbox. Whenever the selectedvalue is changed it should update WebPart C. This is the declaration of the control.

_documentTypeList = new DropDownList();
_documentTypeList.AutoPostBack = true;
this.Controls.Add(_documentTypeList);

The problem here is that using

_documentTypeList.AutoPostBack = true;

reloads the complete page and resets the value in WebPart A to null. How do i send WebPart B's new value to WebPart C without losing the value of WebPart A? This all happens on 1 page.

Answer 1

saving session state varibles can be done using:

    public string Name
    {
        get
        {
            return Page.Session["SaveName"] as string;
        }
        set
        {
            Page.Session["SaveName"] = value;
        }
    }

this is a getter/setter to save/get from session state

to use this do the following:

this gets the value from session state (needs to be in onPreRender event to see session state varibles)

txtName.Text = Name;

this sets into session state (can be anywhere you want to save to session state)

Name = txtName.Text;

for int valuse:

cahnge public string Name to public int Name and same goes for anything else like bool values ect.

so it would look like this for int:

    public int Name
    {
        get
        {
            return Page.Session["SaveName"] as int;
        }
        set
        {
            Page.Session["SaveName"] = value;
        }
    }

As others have noted for data to be passed between webpart you should be using the iInterface method:

provide (webpart sending data) consumer (webpart using that data) and interface that is the connection between the webparts:

the above will 100% work and save your values on postback :)

just incase you need this ;) iv posted some links on connections below.

Connectable WebPart Problems......................?

and

Connection between 2 web parts

hope it helps :)

Answer 2

Have you tried if (!Page.IsPostBack) { your code here } ?

Answer 3

Have you tried creating custom web part connection for your purpose? Going through your requirement may be that's the most appropriate option

Answer 4

Previously the web parts where connected with in the following order.

WebPart A => WebPart B
WebPart B => WebPart C
WebPart A => WebPart C

this created an error if i wanted to call both values in WebPart C when i changed the value in WebPart B. Whenever WebPart B's value was changed it was required to reload the page and therfore reloading WebPart A. Because WebPart A had a value which is created on user interaction and not on page load the value was lost. WebPart B and WebPart C seized to function without the value of WebPart A. If you wish to keep the WebPart Connection as described above please check almostSharePointMaster's answer.

Because in my case WebPart A creates a unique login token i'd rather not save it to the page. I'd prefer keeping it withing the WebParts. To do so i changed the connection between them. Instead above connection i used the following connection.

WebPart A => WebPart B => WebPart C

Webpart B saves the value of WebPart A and provides it together with his own value to WebPart C. This is how WebParts B Interface currently looks like.

public interface IWebPartB
{
    string webPartAValue { get; }
    string webPartBValue { get; }
}