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IDataContractSurrogate Interface

Provides the methods needed to substitute one type for another by the DataContractSerializer during serialization, deserialization, and export and import of XML schema documents (XSD).

Namespace:  System.Runtime.Serialization
Assembly:  System.Runtime.Serialization (in System.Runtime.Serialization.dll)

public interface IDataContractSurrogate

The IDataContractSurrogate type exposes the following members.

  NameDescription
Public methodGetCustomDataToExport(MemberInfo, Type)During schema export operations, inserts annotations into the schema for non-null return values.
Public methodGetCustomDataToExport(Type, Type)During schema export operations, inserts annotations into the schema for non-null return values.
Public methodGetDataContractTypeDuring serialization, deserialization, and schema import and export, returns a data contract type that substitutes the specified type.
Public methodGetDeserializedObjectDuring deserialization, returns an object that is a substitute for the specified object.
Public methodGetKnownCustomDataTypesSets the collection of known types to use for serialization and deserialization of the custom data objects.
Public methodGetObjectToSerializeDuring serialization, returns an object that substitutes the specified object.
Public methodGetReferencedTypeOnImportDuring schema import, returns the type referenced by the schema.
Public methodProcessImportedTypeProcesses the type that has been generated from the imported schema.
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Use the IDataContractSurrogate when using the DataContractSerializer if you need to do one of the following: substitute one type or object for another, or to dynamically generate schema variations. For a sample application, see DataContract Surrogate. For more information about data contracts, see Using Data Contracts.

At run time, you can find the specific DataContractSerializer for any operation in a service by using the OperationDescription to find the DataContractSerializerOperationBehavior instance. For more information about implementing the interface to create a surrogate, see Data Contract Surrogates.

You can also use the IDataContractSurrogate to affect the import and export of XML schemas when you are using the XsdDataContractExporter and XsdDataContractImporter classes. You can do so by assigning the IDataContractSurrogate to the DataContractSurrogate property of the ExportOptions class, or to the DataContractSurrogate property of the ImportOptions class. For more information, see Schema Import and Export.

The following example shows an implementation of the IDataContractSurrogate interface. The code substitutes the serialization of the Person type for a PersonSurrogated class.


class program
{
    static void Main(string[] args)
    {
        SerializeWithSurrogate("surrogateEmployee.xml");
        DeserializeSurrogate("surrogateEmployee.xml");
        // Create an XmlSchemaSet to hold schemas from the 
        // schema exporter.  
        //XmlSchemaSet schemas = new XmlSchemaSet(); 
        //ExportSchemas("surrogateEmployee.xml", ref schemas);
        //// Pass the schemas to the importer. 
        //ImportSchemas(schemas);

    }


    static  DataContractSerializer CreateSurrogateSerializer()  
    {
        // Create an instance of the DataContractSerializer. The  
        // constructor demands a knownTypes and surrogate.  
        // Create a Generic List for the knownTypes. 
        List<Type> knownTypes = new List<Type>();
        LegacyPersonTypeSurrogate surrogate = new LegacyPersonTypeSurrogate ();
        DataContractSerializer surrogateSerializer = 
            new DataContractSerializer(typeof(Employee), 
           knownTypes, Int16.MaxValue, false, true, surrogate);
        return surrogateSerializer;
    }

    static void SerializeWithSurrogate(string filename )
    {
        // Create and populate an Employee instance.
        Employee emp = new Employee();
        emp.date_hired = new DateTime(1999, 10, 14);
        emp.salary = 33000;

        // Note that the Person class is a legacy XmlSerializable class 
        // without a DataContract.
        emp.person = new Person();
        emp.person.first_name = "Mike";
        emp.person.last_name = "Ray";
        emp.person.age = 44;

        // Create a new writer. Then serialize with the  
        // surrogate serializer.
        FileStream  fs =new FileStream(filename, FileMode.Create);
        DataContractSerializer surrogateSerializer = CreateSurrogateSerializer();
        try{
            surrogateSerializer.WriteObject(fs, emp);
            Console.WriteLine("Serialization succeeded. ");
            fs.Close();
        }
        catch (SerializationException exc )
            {
            Console.WriteLine(exc.Message);
            }

    }

    static void DeserializeSurrogate( string filename )
    {
        // Create a new reader object.
        FileStream fs2 = new FileStream(filename, FileMode.Open);
        XmlDictionaryReader reader = 
            XmlDictionaryReader.CreateTextReader(fs2, new XmlDictionaryReaderQuotas());

        Console.WriteLine("Trying to deserialize with surrogate.");
        try
        {
            DataContractSerializer surrogateSerializer = CreateSurrogateSerializer();
            Employee newemp = (Employee) surrogateSerializer.ReadObject(reader, false);

            reader.Close();
            fs2.Close();

            Console.WriteLine("Deserialization succeeded. \n\n");
            Console.WriteLine("Deserialized Person data: \n\t {0} {1}",
                    newemp.person.first_name, newemp.person.last_name);
                Console.WriteLine("\t Age: {0} \n", newemp.person.age);
            Console.WriteLine("\t Date Hired: {0}", newemp.date_hired.ToShortDateString());
            Console.WriteLine("\t Salary: {0}", newemp.salary);
            Console.WriteLine("Press Enter to end or continue");
            Console.ReadLine();
        }
        catch (SerializationException serEx  )
        {
            Console.WriteLine(serEx.Message);
            Console.WriteLine(serEx.StackTrace);
        }

    }

    static void ExportSchemas(string filename , ref XmlSchemaSet schemas)
{
        Console.WriteLine("Now doing schema export.");
        // The following code demonstrates schema export with a surrogate. 
        // The surrogate indicates how to export the non-DataContract Person type. 
        // Without the surrogate, schema export would fail.
        XsdDataContractExporter xsdexp = new XsdDataContractExporter();
        xsdexp.Options = new ExportOptions();
        xsdexp.Options.DataContractSurrogate = new LegacyPersonTypeSurrogate();
        xsdexp.Export(typeof(Employee));

        // Write out the exported schema to a file. 
        using (FileStream fs3 = new FileStream("sample.xsd", FileMode.Create))
        {
            foreach (XmlSchema sch in xsdexp.Schemas.Schemas())
            {
                sch.Write(fs3);
            }
        } 
    }

    static void ImportSchemas(XmlSchemaSet schemas ){
        Console.WriteLine("Now doing schema import.");
        // The following code demonstrates schema import with  
        // a surrogate. The surrogate is used to indicate that  
        // the Person class already exists and that there is no  
        // need to generate a new class when importing the 
        // PersonSurrogated data contract. If the surrogate  
        // was not used, schema import would generate a  
        // PersonSurrogated class, and the person field  
        // of Employee would be imported as  
        // PersonSurrogated and not Person.
        XsdDataContractImporter xsdimp = new XsdDataContractImporter();
        xsdimp.Options = new ImportOptions();
        xsdimp.Options.DataContractSurrogate = new LegacyPersonTypeSurrogate();
        xsdimp.Import(schemas);

        // Write out the imported schema to a C-Sharp file. 
        // The code contains data contract types.
        FileStream fs4 = new FileStream("sample.cs", FileMode.Create);
        try
        {
            StreamWriter tw = new StreamWriter(fs4);
            Microsoft.CSharp.CSharpCodeProvider cdp = new Microsoft.CSharp.CSharpCodeProvider();
            cdp.GenerateCodeFromCompileUnit(xsdimp.CodeCompileUnit, tw, null);
            tw.Flush();
        }
        finally
        {
            fs4.Dispose();
        }


        Console.WriteLine( "\t  To see the results of schema export and import,");
        Console.WriteLine(" see SAMPLE.XSD and SAMPLE.CS." );

        Console.WriteLine(" Press ENTER to terminate the sample." );
        Console.ReadLine();
    }


}


// This is the Employee (outer) type used in the sample.

[DataContract()] 
public class Employee
{
    [DataMember()] 
    public DateTime date_hired ;

    [DataMember()]
public decimal salary ;

    [DataMember()]
    public Person person;
}


// This is the Person (inner) type used in the sample. 
// Note that it is a legacy XmlSerializable type and not a DataContract type. 

public class Person
{
    [XmlElement("FirstName")]
    public string first_name ;

    [XmlElement("LastName")]
    public string last_name ;

    [XmlAttribute("Age")]
    public Int16 age ;

    public Person()  {}   
}

// This is the surrogated version of the Person type 
// that will be used for its serialization/deserialization.

[DataContract] class PersonSurrogated
{
    // xmlData will store the XML returned for a Person instance  
    // by the XmlSerializer.
    [DataMember()]
    public string xmlData;

}

 //This is the surrogate that substitutes PersonSurrogated for Person. 
public class LegacyPersonTypeSurrogate:IDataContractSurrogate
{
    public Type GetDataContractType(Type type) 
{
        Console.WriteLine("GetDataContractType invoked");
        Console.WriteLine("\t type name: {0}", type.Name);
        // "Person" will be serialized as "PersonSurrogated" 
        // This method is called during serialization, 
        // deserialization, and schema export. 
        if (typeof(Person).IsAssignableFrom(type)) 
{
Console.WriteLine("\t returning PersonSurrogated");
            return typeof(PersonSurrogated);
        }
        return type;

    }

public object GetObjectToSerialize(object obj, Type targetType)
{ 
        Console.WriteLine("GetObjectToSerialize Invoked");
        Console.WriteLine("\t type name: {0}", obj.ToString());
        Console.WriteLine("\t target type: {0}", targetType.Name);
        // This method is called on serialization. 
        // If Person is not being serialized... 
        if (obj is Person )
        {
            Console.WriteLine("\t returning PersonSurrogated");
            // ... use the XmlSerializer to perform the actual serialization.
            PersonSurrogated  ps = new PersonSurrogated();
            XmlSerializer xs = new XmlSerializer(typeof(Person));
            StringWriter sw = new StringWriter();
            xs.Serialize(sw, (Person)obj );
            ps.xmlData = sw.ToString();
            return ps;
        }
        return obj;

    }

    public object GetDeserializedObject(Object obj , Type targetType) 
    {
        Console.WriteLine("GetDeserializedObject invoked");
        // This method is called on deserialization. 
        // If PersonSurrogated is being deserialized... 
        if (obj is PersonSurrogated)
            {
                //... use the XmlSerializer to do the actual deserialization.
                PersonSurrogated ps = (PersonSurrogated)obj;
                XmlSerializer xs = new XmlSerializer(typeof(Person));
                return (Person)xs.Deserialize(new StringReader(ps.xmlData));
            }
            return obj;

    }

    public Type GetReferencedTypeOnImport(string typeName,
        string typeNamespace, object customData)
    {
        Console.WriteLine("GetReferencedTypeOnImport invoked");
        // This method is called on schema import. 
        // If a PersonSurrogated data contract is  
        // in the specified namespace, do not create a new type for it  
        // because there is already an existing type, "Person".
        Console.WriteLine( "\t Type Name: {0}", typeName);

        if (typeName.Equals("PersonSurrogated") )
        {
            Console.WriteLine("Returning Person");
            return typeof(Person);
        }        
        return null;
    }

    public System.CodeDom.CodeTypeDeclaration ProcessImportedType(
        System.CodeDom.CodeTypeDeclaration typeDeclaration, 
        System.CodeDom.CodeCompileUnit compileUnit)
    {
        // Console.WriteLine("ProcessImportedType invoked")
        // Not used in this sample. 
        // You could use this method to construct an entirely new CLR  
        // type when a certain type is imported, or modify a  
        // generated type in some way. 
        return typeDeclaration;
    }



        public object GetCustomDataToExport(Type clrType, Type dataContractType)
        {
            // Not used in this sample 
            return null;
        }

        public object GetCustomDataToExport(System.Reflection.MemberInfo memberInfo, Type dataContractType)
        {
            // Not used in this sample 
            return null;
        }

        public void GetKnownCustomDataTypes(Collection<Type> customDataTypes)
        {
            // Not used in this sample
        }
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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