<form id="frm" runat="server">
     <div>
         <asp:GridView ID="gv1" runat="server" AutoGenerateColumns="true"></asp:GridView>
     </div>
 </form> 				

using System;  public class Person {     public string FirstName { get; set; }     public string LastName { get; set; } } 

using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls;  public partial class Default : System.Web.UI.Page {     private List<Person> GetPersons()     {         var personList = new List<Person>();          personList.Add(new Person { FirstName = "Phat", LastName = "Ly" });         personList.Add(new Person { FirstName = "Lam", LastName = "Ly" });         personList.Add(new Person { FirstName = "Tam", LastName = "Chieu" });          personList.Add(new Person { FirstName = "Phuc", LastName = "To" });         personList.Add(new Person { FirstName = "Phuong", LastName = "Tran" });         personList.Add(new Person { FirstName = "Phuong", LastName = "Pham" });          personList.Add(new Person { FirstName = "Phuong", LastName = "Nguyen" });         personList.Add(new Person { FirstName = "Khanh", LastName = "Pham" });         personList.Add(new Person { FirstName = "Viet", LastName = "Pham" });          personList.Add(new Person { FirstName = "Minh", LastName = "Ly" });         return personList;     }      protected void Page_Load(object sender, EventArgs e)     {         if (!Page.IsPostBack)         {             gv1.DataSource = GetPersons();             gv1.DataBind();         }     } } 

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="ViewStateWebApplication.Default" EnableViewStateMac="true" %> 

<configuration>     <system.web>        <pages viewStateEncryptionMode="Always"/>     </system.web> </configuration> 

namespace ViewStateOptimizer {     /// <summary>     /// This interface defines the implements for optimizing the ViewState.     /// </summary>     public interface IViewStateOptimizer     {         /// <summary>         /// Loads the ViewState contents.         /// </summary>         void Load();          /// <summary>         /// Saves the ViewState contents.         /// </summary>         void Save();     } } 

namespace ViewStateOptimizer {     using System;     using System.Web.UI;      /// <summary>     /// This abstract class implements as base class for implementing the custom page state persister.     /// </summary>     public abstract class BaseViewStateOptimizer : PageStatePersister, IViewStateOptimizer     {         protected BaseViewStateOptimizer(Page page)             : base(page)         {         }          /// <summary>         /// Loads the ViewState contents into a string.         /// </summary>         /// <returns>Returns the ViewState contents</returns>         public abstract string LoadViewStateContents();          /// <summary>         /// Saves the ViewState contents.         /// </summary>         /// <param name="viewStateContents">ViewState contents</param>         /// <returns>Returns true if saving OK, otherwise will be false</returns>         public abstract bool SaveViewStateContents(string viewStateContents);          /// <summary>         /// Loads the ViewState contents into ViewState and ControlState.         /// </summary>         public override void Load()         {             IStateFormatter formatter = this.StateFormatter;             var viewStateContents = LoadViewStateContents();             var statePair = (Pair)formatter.Deserialize(viewStateContents);             if (Page.Session != null)             {                 if (statePair != null)                 {                     this.ViewState = statePair.First;                     this.ControlState = statePair.Second;                 }             }             else             {                 throw new InvalidOperationException("The Session is required for ViewStateOptimizer.");             }         }          /// <summary>         /// Saves the ViewState contents.         /// </summary>         public override void Save()         {             if (ViewState != null || ControlState != null)             {                 if (Page.Session != null)                 {                     // --- Serialize the ViewState contents into a string                     var formatter = this.StateFormatter;                     var statePair = new Pair(ViewState, ControlState);                     var serializedState = formatter.Serialize(statePair);                     // --- End                      // Saves to the ViewSate contents with the specified string                     if (!SaveViewStateContents(serializedState))                     {                         throw new InvalidOperationException("Can't save the ViewState contents to the specified location. Please ensure all configurations are correct.");                     }                 }                 else                 {                     throw new InvalidOperationException("The Session is required for ViewStateOptimizer.");                 }             }         }     } } 

namespace ViewStateOptimizer.FileStorage {     using System;     using System.IO;     using System.Security.Cryptography;     using System.Text;     using System.Web.UI;      /// <summary>     /// This class implements storing the ViewState contents in the files.     /// </summary>     public class FileViewStateOptimizer : BaseViewStateOptimizer     {         public FileViewStateOptimizer(Page page)             : base(page)         {         }          /// <summary>         /// Load the ViewState contents into string using the Session for storing the file path.         /// </summary>         /// <returns>Returns the ViewState contents</returns>         public override string LoadViewStateContents()         {             // Don't make anything at the first postback             if (!Page.IsPostBack) return null;              // Get the hashed key from the form             string vsHashedKey = Page.Request.Form[FileViewStateOptimizerOptions.ViewStateKey];              // Checks the existed the hashed key or not?             if (String.IsNullOrEmpty(vsHashedKey) ||                 !vsHashedKey.StartsWith(FileViewStateOptimizerOptions.ViewStatePrefixValue))             {                 throw new ViewStateException();             }              // --- Gets the file path which stored the ViewState contents.             IStateFormatter frmt = StateFormatter;             var salt = Page.Session[vsHashedKey].ToString();             var vsFile = Page.Session[ViewStateOptimizerSecurity.GenerateHashStringBySalt(vsHashedKey, salt)].ToString();             // --- End              // --- Reads the file and return all ViewState contents             if (!String.IsNullOrEmpty(vsFile))             {                 if (File.Exists(vsFile))                 {                     return File.ReadAllText(vsFile);                 }             }             // --- End              return null;         }          /// <summary>         /// Save the ViewState contents to the specified file path which stored in the Session.         /// </summary>         /// <param name="viewStateContents">ViewState contents</param>         /// <returns>Returns true if saving OK, otherwise will be false</returns>         public override bool SaveViewStateContents(string viewStateContents)         {             try             {                 if (ViewState != null || ControlState != null)                 {                     // Checks the existed session or not?                     if (Page.Session == null)                     {                         throw new InvalidOperationException("Session is required for FilePageStatePersister.");                     }                      string vsFile, vsHashedKey, salt;                      if (!Page.IsPostBack) // For the first postback                     {                         // --- Create the unique key for each session each user                         var sessionId = Page.Session.SessionID;                         var pageUrl = Page.Request.Path;                         var vsKey = string.Format("{0}_{1}_{2}_{3}", Guid.NewGuid(), pageUrl, sessionId,                             DateTime.Now.Ticks);                         vsKey = vsKey.Replace("/", String.Empty);                         var vsFileName = vsKey   ".vso";                         // --- End                          // --- Create a new directory with the specified path if no exists.                         var vsPath = Page.MapPath(FileViewStateOptimizerOptions.ViewStateStorageRelativeFolder);                         if (!Directory.Exists(vsPath))                         {                             Directory.CreateDirectory(vsPath);                         }                         vsFile = Path.Combine(vsPath, vsFileName);                         // --- End                          // --- Create new session based upon hash key to secure the viewstate contents                         vsHashedKey = FileViewStateOptimizerOptions.ViewStatePrefixValue   "_"   Convert.ToBase64String(ViewStateOptimizerSecurity.GenerateHash(vsKey));                         salt = ViewStateOptimizerSecurity.GenerateSaltString(50);                         Page.Session[vsHashedKey] = salt;                         Page.Session[ViewStateOptimizerSecurity.GenerateHashStringBySalt(vsHashedKey, salt)] = vsFile;                         // --- End                     }                     else // For the postbacks later                     {                         // --- Gets the hashed key from the form                         vsHashedKey = Page.Request.Form[FileViewStateOptimizerOptions.ViewStateKey];                         if (String.IsNullOrEmpty(vsHashedKey))                         {                             throw new ViewStateException();                         }                         // --- End                          // --- Gets the specified file path which stored in the Session                         salt = Page.Session[vsHashedKey].ToString();                         vsFile = Page.Session[ViewStateOptimizerSecurity.GenerateHashStringBySalt(vsHashedKey, salt)].ToString();                         if (string.IsNullOrEmpty(vsFile))                         {                             throw new ViewStateException();                         }                         // --- End                     }                      // Write all ViewState contents to the specified file                     File.WriteAllText(vsFile, viewStateContents);                      // Register a new hidden field to the client-side with the ViewState key and hashed key                     Page.ClientScript.RegisterHiddenField(FileViewStateOptimizerOptions.ViewStateKey, vsHashedKey);                      return true;                 }                 return false;             }             catch             {                 return false;             }         }     } } 

namespace ViewStateOptimizer.FileStorage {     using System;     using System.IO;     using System.Web;      /// <summary>     /// This abstract class implements removing the *.vso files that store the ViewState contents.     /// Be able to inherit this class to implement your custom own.     /// </summary>     public abstract class BaseFileViewStateOptimizerHttpApplication : HttpApplication     {         /// <summary>         /// This event will be fired and then will remove the *.vso files that store the ViewState contents         /// when the session timeout has expired.         /// </summary>         /// <param name="sender">object that raised this event</param>         /// <param name="e">event data</param>         protected virtual void Session_End(object sender, EventArgs e)         {             // --- Remove the *.vso files that store the ViewState contents.             foreach (string key in Session.Keys)             {                 if(key.StartsWith(FileViewStateOptimizerOptions.ViewStatePrefixValue))                 {                     var salt = Session[key].ToString();                     var vsFile = Session[ViewStateOptimizerSecurity.GenerateHashStringBySalt(key, salt)].ToString();                     if(File.Exists(vsFile))                     {                         File.Delete(vsFile);                     }                 }             }             // --- End         }     } } 

namespace ViewStateOptimizer {     using System;     using System.Security.Cryptography;     using System.Text;      /// <summary>     /// This static class contains the useful helpers to secure the configurations for ViewState     /// </summary>     public static class ViewStateOptimizerSecurity     {         /// <summary>         /// Standardize from byte array to the UTF-8 string.         /// </summary>         /// <param name="bytes">byte array</param>         /// <returns>Returns the UTF-8 string</returns>         public static string StandardizeToUtf8String(byte[] bytes)         {             return Encoding.UTF8.GetString(bytes);         }          /// <summary>         /// Standardize from string to byte array.         /// </summary>         /// <param name="value">string</param>         /// <returns>Returns the byte array</returns>         public static byte[] StandardizeToUtf8Bytes(string value)         {             return Encoding.UTF8.GetBytes(value);         }          /// <summary>         /// Generates the salt byte array with the specified salt size.         /// </summary>         /// <param name="saltSize">salt size</param>         /// <returns>Return the salt byte array</returns>         public static byte[] GenerateSalt(int saltSize)         {             HashAlgorithm algorithm = new SHA512Managed();              byte[] random = new Byte[saltSize];             RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();             rng.GetBytes(random);              return algorithm.ComputeHash(random);         }          /// <summary>         /// Generates the salt string with the specified salt size.         /// </summary>         /// <param name="saltSize">salt size</param>         /// <returns>Return the salt string</returns>         public static string GenerateSaltString(int saltSize)         {             return StandardizeToUtf8String(GenerateSalt(saltSize));         }          /// <summary>         /// Generates the hash byte array with the specified value.         /// </summary>         /// <param name="value">string</param>         /// <returns>Returns the hash byte array</returns>         public static byte[] GenerateHash(string value)         {             HashAlgorithm algorithm = new SHA512Managed();             return algorithm.ComputeHash(Encoding.Default.GetBytes(value));         }          /// <summary>         /// Generates the hashed byte array with the specified value and salt string.         /// </summary>         /// <param name="value">hash string</param>         /// <param name="salt">salt string</param>         /// <returns>Returns the hashed byte array</returns>         public static byte[] GenerateHashBySalt(string value, string salt)         {             var hmacSHA512 = new HMACSHA512(StandardizeToUtf8Bytes(salt));             return hmacSHA512.ComputeHash(StandardizeToUtf8Bytes(value));         }          /// <summary>         /// Generates the hashed string with the specified value and salt string.         /// </summary>         /// <param name="value">hash string</param>         /// <param name="salt">salt string</param>         /// <returns>Returns the hashed string</returns>         public static string GenerateHashStringBySalt(string value, string salt)         {             return StandardizeToUtf8String(GenerateHashBySalt(value, salt));         }     } } 

namespace ViewStateOptimizer.FileStorage {     using System.Web.UI;     using System.Web.UI.Adapters;      /// <summary>     /// This class implements customizing the default PageStatePersister to FileViewStateOptimizer.     /// </summary>     public class FileViewStateOptimizerPageAdapter : PageAdapter     {         /// <summary>         /// Gets the file state persister.         /// </summary>         /// <returns>Returns the PageStatePersister type as FileViewStateOptimizer</returns>         public override PageStatePersister GetStatePersister()         {             return (new FileViewStateOptimizer(this.Page));         }     } } 

namespace ViewStateOptimizer {     using System.Web.UI;     using System.Web.UI.Adapters;      /// <summary>     /// This class implements customizing the default PageStatePersister to SessionViewStateOptimizer.     /// </summary>     public class SessionViewStateOptimizerPageAdapter : PageAdapter     {         /// <summary>         /// Gets the session state persister.         /// </summary>         /// <returns>Returns the PageStatePersister type as SessionPageStatePersister</returns>         public override PageStatePersister GetStatePersister()         {             return (new SessionPageStatePersister(this.Page));         }     } } 

Thư viện này mình viết trên nền .NET Framework 2.0 và có thể giải quyết các bất lợi trên. Vì thế ứng dụng asp.net web forms của bạn phải >= .Net Framework 2.0.

Kết luận

Mình hy vọng qua chủ đề này ViewState sẽ không còn là cơn ác mộng đối với nhiều lập trình viên asp.net web forms. Chúng ta có thể lưu trữ và tải dữ liệu ViewState trên server với nhiều giải pháp khác nhau. Các bạn có thể tải source code thư viện ở dưới đây

Download source code thư viện ViewStateOptimizer trên Github
Download source code thư viện ViewStateOptimizer trên Codeplex

Nếu có gì sai sót, mong các bạn góp ý để hoàn thiện hơn.