如何序列化ViewState对象

Question

I have some functions that query a database and puts the result into a gridview. It also sets a ViewState variable that contains the results of the query. When I postback, I have a load function that loads the gridview from the last results if any.

The Problem I am having is that I am getting an error that basically says that the viewstate object needs to be serialized. From what I have I am not sure how to do this.

Error: Sys.WebForms.PageRequestManagerServerErrorException: Error serializing value 'System.Collections.Generic.List 1[<>f__AnonymousType17 2[System.Int32,System.String]]' of type 'System.Collections.Generic.List 1[[<>f__AnonymousType17 2[[System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]], App_Web_rjb524gi, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null]].'

My code so far:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Runtime.Serialization;

public partial class PlayersManagement : System.Web.UI.Page
{ 

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

public void LoadData()
{

    if (ViewState["CurrentGridView"] != null || ViewState["CurrentGridView"] == "")
    {
        GridViewPlayers.DataSource = ViewState["CurrentGridView"];
        GridViewPlayers.DataBind();
    }
    else
    {

        DBModel.DBEntities context = new  DBModel.DBEntities();

        var players= (from f in context.Players
                        where f.isDeleted == false
                        select new
                        {
                            f.PlayerId,
                            f.PlayerName

                        }).ToList();

        GridViewPlayers.DataSource = players;
        GridViewPlayers.DataBind();
    }

    ViewState["Sort"] = 0;

}


/**
   * This method is for advance search functionality 
   * 
   */
protected void btnSearch_Click(object sender, EventArgs e)
{

    // If the search textbox is not empty
    if (txtSearch.Text.Trim() != "")
    {
        // Call to Entity Model Framework
       DBModel.DBEntities context = new DBModel.DBEntities();

        //Querying the Players table 
        var search = (from s in context.Players
                      where s.PlayerName.Contains(txtSearch.Text.Trim())
                      select new
                      {
                          s.PlayerId,
                          s.PlayerName

                      }).ToList();


        if (search.Count != 0)
        {

            noResults.Visible = false;

            GridViewPlayers.DataSource = search;//Connecting query to the datasource Gridview

            ViewState["CurrentGridView"] = search; // <---- Error cause here

            GridViewPlayers.DataBind();  //Binding Gridview
        }
        else
        {
            noResults.Visible = true;
            noResults.Text = "This '" + txtSearch.Text + "' Query Returned No Results";

            txtSearch.Text = "";

        }


    }

}


 protected void Gridview_Sort(object sender, GridViewSortEventArgs e)
{

    //Label2.Text = e.SortExpression + " " + ConvertSortDirectionToSql(e.SortDirection);
     DBModel.DBEntities context = new  DBModel.DBEntities();

    var players = (from b in context.Players
                 where b.isDeleted == false
                 select b);

    DataTable gridviewTable = players.CopyToDataTable();

    gridviewTable.DefaultView.Sort = e.SortExpression + " " + ConvertSortDirectionToSql(e.SortDirection);

    GridViewPlayers.DataSource = gridviewTable;

    ViewState["CurrentGridView"] = gridviewTable; <--- Also causes error

    GridViewPlayers.DataBind();

}


private string ConvertSortDirectionToSql(SortDirection sortDirection)
{
    string newSortDirection = String.Empty;

    int sort = (ViewState["Sort"] == null) ? 0 : (int)ViewState["Sort"];
    switch (sort)
    {
        case 0:
            newSortDirection = "ASC";
            ViewState["Sort"] = 1;
            break;

        case 1:
            newSortDirection = "DESC";
            ViewState["Sort"] = 0;
            break;
    }

    return newSortDirection;
}

protected void GridViewPlayers_RowEditing(object sender, GridViewEditEventArgs e)
{
    GridViewPlayers.EditIndex = e.NewEditIndex;
    LoadData();
}


protected void GridViewPlayers_CancelEditRow(object sender, GridViewCancelEditEventArgs e)
{
    GridViewPlayers.EditIndex = -1;
    LoadData();
}

Answer 1

If you really want to store it in View State then you will probably want to have a type that can be marked as [Serializable] . It looks like the anonymous type is not. So instead of using:

var search

use

 List<Player> search =  Query  

And the class.

[Serializable]
public class Player
{
    public int PlayerId {get;set;}
    public string PlayerName {get;set;}
}

However, It looks like you are querying the db each time, so even if you did store in viewstate you wouldnt be gaining anything.

Answer 2

The problem is, that you can't pass anonymous objects using the ViewState . One solution would be to create strongly typed models and use them instead the anonymous objects. Create a Player class:

public class Player
{
    public Int32 PlayerId { get; set; }
    public String PlayerName { get; set; }
}

and use it like this:

var search = (from s in context.Players
    where s.PlayerName.Contains(txtSearch.Text.Trim())
    select new Player
    {
        PlayerId = s.PlayerId,
        PlayerName = s.PlayerName

    }).ToList();

instead of:

var search = (from s in context.Players
    where s.PlayerName.Contains(txtSearch.Text.Trim())
    select new
    {
        s.PlayerId,
        s.PlayerName

    }).ToList();

Do this for all your dynamic results (change them to use concrete classes) and the binding resp. serialization resp. passing via ViewState should work properly.