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Classe JavaScriptSerializer

 

Data di pubblicazione: ottobre 2016

Json.NET deve essere usato per la serializzazione e deserializzazione. Fornisce funzionalità di serializzazione e deserializzazione per le applicazioni con supporto AJAX.

Spazio dei nomi:   System.Web.Script.Serialization
Assembly:  System.Web.Extensions (in System.Web.Extensions.dll)

System.Object
  System.Web.Script.Serialization.JavaScriptSerializer

public class JavaScriptSerializer

NomeDescrizione
System_CAPS_pubmethodJavaScriptSerializer()

Inizializza una nuova istanza della classe JavaScriptSerializer che non possiede un resolver di tipi.

System_CAPS_pubmethodJavaScriptSerializer(JavaScriptTypeResolver)

Inizializza una nuova istanza della classe JavaScriptSerializer che possiede un resolver di tipi personalizzato.

NomeDescrizione
System_CAPS_pubpropertyMaxJsonLength

Ottiene o imposta la lunghezza massima delle stringhe JSON accettate dalla classe JavaScriptSerializer.

System_CAPS_pubpropertyRecursionLimit

Ottiene o imposta il limite per vincolare il numero di livelli dell'oggetto da elaborare.

NomeDescrizione
System_CAPS_pubmethodConvertToType(Object, Type)

Converte l'oggetto indicato nel tipo specificato.

System_CAPS_pubmethodConvertToType<T>(Object)

Converte l'oggetto specificato nel tipo specificato.

System_CAPS_pubmethodDeserialize(String, Type)

Converte una stringa in formato JSON in un oggetto del tipo specificato.

System_CAPS_pubmethodDeserialize<T>(String)

Converte la stringa JSON specificata in un oggetto di tipo T.

System_CAPS_pubmethodDeserializeObject(String)

Converte la stringa JSON specificata in un oggetto grafico.

System_CAPS_pubmethodEquals(Object)

Determina se l'oggetto specificato è uguale all'oggetto corrente.(Ereditato da Object.)

System_CAPS_protmethodFinalize()

Consente a un oggetto di effettuare un tentativo di liberare risorse ed eseguire altre operazioni di pulizia prima che venga recuperato da Garbage Collection.(Ereditato da Object.)

System_CAPS_pubmethodGetHashCode()

Funge da funzione hash predefinita.(Ereditato da Object.)

System_CAPS_pubmethodGetType()

Ottiene l'oggetto Type dell'istanza corrente.(Ereditato da Object.)

System_CAPS_protmethodMemberwiseClone()

Crea una copia superficiale dell'oggetto Object corrente.(Ereditato da Object.)

System_CAPS_pubmethodRegisterConverters(IEnumerable<JavaScriptConverter>)

Registra un convertitore personalizzato con l'istanza JavaScriptSerializer.

System_CAPS_pubmethodSerialize(Object)

Converte un oggetto in una stringa JSON.

System_CAPS_pubmethodSerialize(Object, StringBuilder)

Serializza un oggetto e scrive la stringa JSON risultante in un oggetto StringBuilder specificato.

System_CAPS_pubmethodToString()

Restituisce una stringa che rappresenta l'oggetto corrente.(Ereditato da Object.)

The T:System.Web.Script.Serialization.JavaScriptSerializer class is used internally by the asynchronous communication layer to serialize and deserialize the data that is passed between the browser and the Web server. You cannot access that instance of the serializer. However, this class exposes a public API. Therefore, you can use the class when you want to work with JavaScript Object Notation (JSON) in managed code.

To serialize an object, use the Overload:System.Web.Script.Serialization.JavaScriptSerializer.Serialize method. To deserialize a JSON string, use the M:System.Web.Script.Serialization.JavaScriptSerializer.Deserialize``1(System.String) or M:System.Web.Script.Serialization.JavaScriptSerializer.DeserializeObject(System.String) methods. To serialize and deserialize types that are not natively supported by T:System.Web.Script.Serialization.JavaScriptSerializer, implement custom converters by using the T:System.Web.Script.Serialization.JavaScriptConverter class. Then register the converters by using the M:System.Web.Script.Serialization.JavaScriptSerializer.RegisterConverters(System.Collections.Generic.IEnumerable{System.Web.Script.Serialization.JavaScriptConverter}) method.

The following table shows the mapping between managed types and JSON for the serialization process. These managed types are natively supported by T:System.Web.Script.Serialization.JavaScriptSerializer. When you are deserializing from a JSON string to a managed type, the same mapping applies. However, deserialization can be asymmetric; not all serializable managed types can be deserialized from JSON.

System_CAPS_noteNota

A multidimensional array is serialized as a one-dimensional array, and you should use it as a flat array.

Managed type

JSON equivalent

String (UTF-8 encoding only).

String

Char

String

Single null char (such as, \0 )

Null

Boolean

Boolean. Represented in JSON as true or false

null (null object references and Nullable value types).

A string value of null

DBNull

A string value of null

Primitive numeric (or numeric-compatible) types: T:System.Byte, T:System.SByte, T:System.Int16, T:System.Int32, T:System.Int64, T:System.UInt16, T:System.UInt32, T:System.UInt64, T:System.Double, and T:System.Single. The culture-invariant string representation is used.

Number

DateTime

Date object, represented in JSON as "\/Date(number of ticks)\/". The number of ticks is a positive or negative long value that indicates the number of ticks (milliseconds) that have elapsed since midnight 01 January, 1970 UTC.

The maximum supported date value is F:System.DateTime.MaxValue (12/31/9999 11:59:59 PM) and the minimum supported date value is F:System.DateTime.MinValue (1/1/0001 12:00:00 AM).

Enumerations of integer type

Integer equivalent of the enumeration value

Types that implement T:System.Collections.IEnumerable or T:System.Collections.Generic.IEnumerable`1 that are not also implementations of T:System.Collections.IDictionary or T:System.Collections.Generic.IDictionary`2. This includes types such as T:System.Array, T:System.Collections.ArrayList, and T:System.Collections.Generic.List`1.

Array that uses JSON array syntax

Types that implement T:System.Collections.IDictionary or T:System.Collections.Generic.IDictionary`2. This includes types such as T:System.Collections.Generic.Dictionary`2 and T:System.Collections.Hashtable.

JavaScript object that uses JSON dictionary syntax

Custom concrete (non-abstract) types that have public instance properties that have get accessors or public instance fields.

Note that public write-only properties, public property or public field attributes marked with T:System.Web.Script.Serialization.ScriptIgnoreAttribute, and public indexed properties in these types are ignored.

JavaScript object that uses JSON dictionary syntax. A special metadata property named "__type" is included to ensure correct deserialization. Make sure that public instance properties have get and set accessors to ensure correct deserialization.

Guid

String representation of a GUID

Uri

String representation of the return value of M:System.Uri.GetComponents(System.UriComponents,System.UriFormat)

The first example provides a simple illustration of how to serialize and deserialize data objects. It requires a class names Person which is shown below.

using System;
using System.Collections.Generic;
using System.Web.UI;
using System.Web.Script.Serialization;

namespace ExampleApplication
{
    public partial class _Default : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            var RegisteredUsers = new List<Person>();
            RegisteredUsers.Add(new Person() { PersonID = 1, Name = "Bryon Hetrick", Registered = true });
            RegisteredUsers.Add(new Person() { PersonID = 2, Name = "Nicole Wilcox", Registered = true });
            RegisteredUsers.Add(new Person() { PersonID = 3, Name = "Adrian Martinson", Registered = false });
            RegisteredUsers.Add(new Person() { PersonID = 4, Name = "Nora Osborn", Registered = false });

            var serializer = new JavaScriptSerializer();
            var serializedResult = serializer.Serialize(RegisteredUsers);
            // Produces string value of:
            // [
            //     {"PersonID":1,"Name":"Bryon Hetrick","Registered":true},
            //     {"PersonID":2,"Name":"Nicole Wilcox","Registered":true},
            //     {"PersonID":3,"Name":"Adrian Martinson","Registered":false},
            //     {"PersonID":4,"Name":"Nora Osborn","Registered":false}
            // ]

            var deserializedResult = serializer.Deserialize<List<Person>>(serializedResult);
            // Produces List with 4 Person objects
        }
    }
}
using System;

namespace ExampleApplication
{
    public class Person
    {
        public int PersonID { get; set; }
        public string Name { get; set; }
        public bool Registered { get; set; }
    }
}

The next example shows a more complicated and complete project that uses the T:System.Web.Script.Serialization.JavaScriptSerializer class to save and restore the state of an object by using JSON serialization. This code uses a custom converter that is provided for the T:System.Web.Script.Serialization.JavaScriptConverter class.

<%@ Page Language="C#" %>
<%@ Import Namespace="System.Web.Script.Serialization" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">

    JavaScriptSerializer serializer;
    protected void Page_Load(object sender, EventArgs e)
    {
        serializer = new JavaScriptSerializer();

        // Register the custom converter.
        serializer.RegisterConverters(new JavaScriptConverter[] { 
            new System.Web.Script.Serialization.CS.ListItemCollectionConverter() });
        this.SetFocus(TextBox1);
    }

    protected void saveButton_Click(object sender, EventArgs e)
    {
        // Save the current state of the ListBox control.
        SavedState.Text = serializer.Serialize(ListBox1.Items);
        recoverButton.Enabled = true;
        Message.Text = "State saved";
    }

    protected void recoverButton_Click(object sender, EventArgs e)
    {        
        //Recover the saved items of the ListBox control.
        ListItemCollection recoveredList = serializer.Deserialize<ListItemCollection>(SavedState.Text);
        ListItem[] newListItemArray = new ListItem[recoveredList.Count];
        recoveredList.CopyTo(newListItemArray, 0);
        ListBox1.Items.Clear();
        ListBox1.Items.AddRange(newListItemArray);
        Message.Text = "Last saved state recovered.";
    }

    protected void clearButton_Click(object sender, EventArgs e)
    {
        // Remove all items from the ListBox control.
        ListBox1.Items.Clear();
        Message.Text = "All items removed";
    }

    protected void ContactsGrid_SelectedIndexChanged(object sender, EventArgs e)
    {
        // Get the currently selected row using the SelectedRow property.
        GridViewRow row = ContactsGrid.SelectedRow;

        // Get the ID of item selected.
        string itemId = ContactsGrid.DataKeys[row.RowIndex].Value.ToString();                
        ListItem newItem = new ListItem(row.Cells[4].Text, itemId);

        // Check if the item already exists in the ListBox control.
        if (!ListBox1.Items.Contains(newItem))
        {
            // Add the item to the ListBox control.
            ListBox1.Items.Add(newItem);
            Message.Text = "Item added";
        }
        else
            Message.Text = "Item already exists";
    }

    protected void ContactsGrid_PageIndexChanged(object sender, EventArgs e)
    {
        //Reset the selected index.
        ContactsGrid.SelectedIndex = -1;
    }

    protected void searchButton_Click(object sender, EventArgs e)
    {
        //Reset indexes.
        ContactsGrid.SelectedIndex = -1;
        ContactsGrid.PageIndex = 0;

        //Set focus on the TextBox control.
        ScriptManager1.SetFocus(TextBox1);
    }

    protected void CheckBox1_CheckedChanged(object sender, EventArgs e)
    {
        // Show/hide the saved state string.        
        SavedState.Visible = CheckBox1.Checked;
        StateLabel.Visible = CheckBox1.Checked;
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Save/Recover state</title>
    <style type="text/css">
        body {  font: 11pt Trebuchet MS;
                font-color: #000000;
                padding-top: 72px;
                text-align: center }

        .text { font: 8pt Trebuchet MS }
    </style>
</head>
<body>    
    <form id="form1" runat="server" defaultbutton="searchButton" defaultfocus="TextBox1">
        <h3>
            <span style="text-decoration: underline">
                                    Contacts Selection</span><br />
        </h3>
        <asp:ScriptManager runat="server" ID="ScriptManager1" />
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
                Type contact's first name:
                <asp:TextBox ID="TextBox1" runat="server" />
                <asp:Button ID="searchButton" runat="server" Text="Search" OnClick="searchButton_Click" />&nbsp;
                <br />
                <br />
                <table border="0" width="100%">
                    <tr>
                        <td style="width:50%" valign="top" align="center">
                            <b>Search results:</b><br />
                            <asp:GridView ID="ContactsGrid" runat="server" AutoGenerateColumns="False"
                                CellPadding="4" DataKeyNames="ContactID" DataSourceID="SqlDataSource1"
                                OnSelectedIndexChanged="ContactsGrid_SelectedIndexChanged" ForeColor="#333333" GridLines="None" AllowPaging="True" PageSize="7" OnPageIndexChanged="ContactsGrid_PageIndexChanged">
                                <Columns>
                                    <asp:CommandField ShowSelectButton="True" ButtonType="Button" />
                                    <asp:BoundField DataField="ContactID" HeaderText="ContactID" SortExpression="ContactID" Visible="False" />
                                    <asp:BoundField DataField="FirstName" HeaderText="FirstName" SortExpression="FirstName" />
                                    <asp:BoundField DataField="LastName" HeaderText="LastName" SortExpression="LastName" />
                                    <asp:BoundField DataField="EmailAddress" HeaderText="EmailAddress" SortExpression="EmailAddress" />
                                </Columns>
                                <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
                                <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
                                <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
                                <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
                                <EditRowStyle BackColor="#999999" />
                                <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
                                <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
                                <EmptyDataTemplate>No data found.</EmptyDataTemplate>
                            </asp:GridView>
                            <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:AdventureWorksConnectionString %>"
                                SelectCommand="SELECT ContactID, FirstName, LastName, EmailAddress FROM Person.Contact WHERE (UPPER(FirstName) = UPPER(@FIRSTNAME))" >
                                <SelectParameters>
                                    <asp:ControlParameter Name="FIRSTNAME" ControlId="TextBox1" Type="String" />
                                </SelectParameters>
                            </asp:SqlDataSource>
                        </td>
                        <td valign="top">
                            <b>Contacts list:</b><br />
                        <asp:ListBox ID="ListBox1" runat="server" Height="200px" Width="214px" /><br />
                        <asp:Button ID="saveButton" runat="server" Text="Save state" OnClick="saveButton_Click" ToolTip="Save the current state of the list" />
                        <asp:Button ID="recoverButton" runat="server" Text="Recover saved state" OnClick="recoverButton_Click" Enabled="false" ToolTip="Recover the last saved state" />
                        <asp:Button ID="clearButton" runat="server" Text="Clear" OnClick="clearButton_Click" ToolTip="Remove all items from the list" /><br />
                            <br />
                            <asp:CheckBox ID="CheckBox1" runat="server" Checked="True" OnCheckedChanged="CheckBox1_CheckedChanged"
                                Text="Show saved state" AutoPostBack="True" /></td>
                    </tr>
                    <tr>
                        <td colspan="2">
                            <br />
                            <br />
                            &nbsp;&nbsp;
                            <hr />
                            Message: <asp:Label ID="Message" runat="server" ForeColor="SteelBlue" />&nbsp;&nbsp;<br />
                            <asp:Label ID="StateLabel" runat="server" Text="State:"></asp:Label>
                            <asp:Label ID="SavedState" runat="server"/><br />                        
                        </td>
                    </tr>
                </table>
            </ContentTemplate>
        </asp:UpdatePanel>
        <asp:UpdateProgress ID="UpdateProgress1" runat="server">
            <ProgressTemplate>
                <asp:Image ID="Image1" runat="server" ImageUrl="..\images\spinner.gif" />&nbsp;Processing...
            </ProgressTemplate>
        </asp:UpdateProgress>
    </form>
</body>
</html>

.NET Framework
Disponibile da 3.5

I membri statici pubblici ( Condiviso in Visual Basic) di questo tipo è thread safe. Non tutti i membri di istanza sono garantiti come thread safe.

Spazio dei nomi System.Web.Script.Serialization
Using Web Services in ASP.NET AJAX
Calling Web Services from Client Script in ASP.NET AJAX

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