Serializing .NET framework types

Article
06/14/2022

In Microsoft .NET Framework, serialization is the process of converting an object into a format that can be transmitted across a network connection. Microsoft .NET Framework interoperability uses serialization for communication between client-side .NET Framework objects and server-side .NET Framework objects. When you configure DotNet variables in a Dynamics 365 Business Central object, you can specify .NET Framework objects to target either the Business Central Windows client or Business Central Server. In some cases, a client-side object and a server-side object must communicate and share data, such as return values and parameters. The serialization occurs when the following conditions are true:

When a server-side object is assigned to a client-side object, and vice-versa.
When a server-side object is passed as a parameter in a method call from the server to a client-side object, and vice-versa.

Serialization requires that the .NET Framework types that are used by the DotNet variables are serializable. Many types in the Microsoft .NET Framework class library are already serializable. If you are using a .NET Framework type that cannot be serialized, then you must modify the type to make it serializable.

Important

For the Business Central Web client, you cannot implement Microsoft .NET Framework interoperability objects that target the client.

Making a type serializable

There are two ways that you can make a .NET Framework type serializable. You can implement basic serialization by applying the System.SerializableAttribute attribute to the type or you can implement custom serialization by using System.Runtime.Serialization.ISerializable interface.

Basic serialization using SerializableAttribute

Basic serialization uses the .NET Framework to automatically serialize an object. To implement basic serialization on a type, you decorate the type with the SerializableAttribute class as shown in the following example.

[Serializable]  
public class MyObject  
{  
    code   
}

This method requires that you have access to the source code of the .NET Framework assembly.

Basic serialization of date fields

You can use basic serialization only if all data fields in the type are serializable. Fields that are calculated at runtime cannot be serialized. If a field cannot be serialized, then at runtime, the serialization process will throw an exception and the AL code execution will fail.

You can exclude fields from the serialization process by decorating the field with the System.NonSerializedAttribute class.

Custom serialization using ISerializable interface

With custom serialization, you can create an object that controls the serialization of types in another object. This method is useful when you do not have access to the source code of the assembly that contains the .NET Framework types that you are implementing with .NET Framework interoperability. The custom object specifies which types will be serialized and how serialization will be done.

To implement custom serialization, you create a class that implements the ISerializable interface, and decorate the class with SerializableAttribute. In most cases, you must also implement the System.Runtime.Serialization.ISerializable.GetObjectData method and a special constructor that is used when the source object is deserialized. You use the GetObjectData method to populate the SerializationInfo the data that is required to serialize the source object at runtime.

The common language runtime calls the constructor during deserialization to construct a replica of the source object. The constructor takes two parameters, a SerializationInfo type and a System.Runtime.Serialization.StreamingContext type. The StreamingContext parameter describes the source and destination of a given serialized stream.

Custom serialization example

The following code example demonstrates a custom serialization object that implements the basic functionality that is required for compliance with the ISerializable interface. In the first procedure of this example, you create a .NET Framework assembly that includes a serializable type. In the second procedure, in the Business Central development environment, you create a codeunit that includes two DotNet variables for the serializable type. You set one variable to target the Business Central Windows client and the other to target the Business Central Server. In AL code, you add code that transfers the value for the DotNet variable on the Business Central Server to the Business Central Windows client. You will also add code that verifies that the data transfer is successful.

To create the custom serialization object

In Microsoft Visual Studio, create a C# Class Library project called SerializationSample.
Add the following code.

 using System;  
 using System.Runtime.Serialization;  

 [Serializable]  
 public class SerializeWithInterface : ISerializable  
 {  
      // Defines a field that will not be serialized.  
      [NonSerialized]  
      private string notSerializedField;  
      // Defines two fields that will be serialized.  
      private int serializedIntField;  
      private string serializedStringField;  
      // Specifies literal field names.  
      private const string serializedIntFieldName = “serializedIntField”;  
      private const string serializedStringFieldName = “serializeStringField”;  

      // Defines a default constructor that initializes the object with default values.  
      public SerializeWithInterface()  
      {  
           this.serializedIntField = 1;  
           this.notSerializedField = string.Empty;  
           this.serializedStringField = string.Empty;  
      }  

      // Defines the protected constructor that is required by the ISerializable interface.  
      // Data is stored in the SerializationInfo argument and is extracted using the GetValue method.  
      protected SerializeWithInterface(SerializationInfo si, StreamingContext context)  
      {  
           this.serializedStringField = (string)si.GetValue(serializedStringFieldName, typeof(string));  
           this.serializedIntField = (int)si.GetValue(serializedIntFieldName, typeof(int));  
      }  

      // Fills the SerializationInfo object with data that must to be sent to the replicated object.  
      // Data is stored in the dictionary using the AddValue method.   
      // The SerializationInfo object is a key/value dictionary.  
      // The name you use to store the value must match the name used in the constructor.  
      // For this reason, a string constant is used.  
      public void GetObjectData(SerializationInfo info, StreamingContext context)  
      {  
           info.AddValue(serializedStringFieldName, this.serializedStringField);  
           info.AddValue(serializedIntFieldName, this.serializedIntField);  
      }  

      // Remaining class implementation is irrelevant for the serialization process.  
      // The SerializedStringField property is used by AL code to verify that the contained data is transferred between the server and client.  
      // SerializedStringField gets or sets the internal serialized string field.  
      public string SerializedStringField  
      {  
           get { return this.serializedStringField; }  
           set { this.serializedStringField = value; }  
      }  
 }

Build the project.
Copy the SerializationSample.dll to the Add-ins folder of the Business Central Windows client and Business Central Server installation folders.

By default, the path of the Business Central Windows client installation folder is C:\Program Files (x86)\Microsoft Dynamics 365 Business Central\210\RoleTailored Client\Add-ins.

By default, the path of the Business Central Server installation folder is C:\Program Files\Microsoft Dynamics 365 Business Central\210\Service\Add-ins.

To test the serialization object

In the AL Development Environment, add the following code.

dotnet
{
     assembly(SerializationSample)
     {
          type(SerializationSample.SerializeWithInterface; SerializeWithInterface){}
     }
}

codeunit 50101 SerializationSample
{
    procedure Testing()
    var
        ServerObject: DotNet SerializeWithInterface;
        ClientObject: DotNet SerializeWithInterface;

    begin
        // Constructor that instantiates the ServerObject object on the server.  
        ServerObject := ServerObject.SerializeWithInterface();  
        // Constructor that instantiates the ClientObject object on the server.  
        ClientObject := ClientObject.SerializeWithInterface();  
        // Assign unique values to the data members in the two objects.  
        ServerObject.SerializedStringField := ‘ServerSide’;  
        ClientObject.SerializedStringField := ‘ClientSide’;  
        // Transfer the server object to the client object using serialization.  
        ClientObject := ServerObject;  
        // Test if the objects contain the same data.  
        If ClientObject.SerializedStringField <> ServerObject.SerializedStringField then  
            Error(‘Client object does not match the server object.’);  
            Message(‘Server data has been serialized to the client object.’);
    end;
}

The line that contains assignment of the ServerObject to the ClientObject causes the serialization process to run. When completed, the message Server data has been serialized to the client object appears, which verifies that the server object has been transferred to the client object.

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