---
title: Creating custom binding classes
related:
  - https://docs.kentico.com/k8/custom-development/creating-custom-modules.md
---

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Binding classes represent relationships between other classes. Add a binding class to your [custom modules](https://docs.kentico.com/k8/custom-development/creating-custom-modules.md) if you need to store M:N relationships between a custom class and another class in the system (custom or default). For example, bindings allow you to assign objects to sites, users, etc.

## Adding binding classes

You can create two types of binding classes:

- [Binding class with its own primary key / identity column](#primary-key-with-identity) (recommended)
- [Binding class with a compound primary key consisting of two or more foreign keys](#compound-primary-key)

**Note**: If you create a binding class between classes of the _same type_, you cannot use the default **Edit bindings** page template and the portal engine to build a binding management interface.

### Primary key with identity

Use the following steps to create a binding class with a dedicated identity column:

1. Open the **Modules** application and edit the custom module where you want to create the binding class.
2. Select the **Classes** tab and click **New class**.
3. Fill in the **Class display name** and **Class** identifier.
4. Click **Next**.
5. Confirm or change the **Primary key name** of the identity column.

   > **Note:** **Important**: Leave the **Is M:N table** option disabled.
6. Click **Next**.
7. Leave the default primary key field. Click **New field** to create _two or more_ standard fields for storing the IDs of the related objects:

   - **Field type**: Standard field
   - **(General) Field type**: Integer number
   - **Required**: yes (checked)
   - **Reference to**: select the appropriate class
   - **Reference type**: Binding
   - **Display field in the editing form**: no (not checked)
8. Click **Save** for each field and then **Next**.
9. Click **Finish**.

The system creates the corresponding table in the database. Perform the following steps to prepare the class's code and finalize the database table:

1. Select the **Code** tab in the editing interface of the binding class.
2. Click **Save code**. The system generates an _Info_ and _InfoProvider_ class for the binding object.
3. Edit the _Info_ class (for example in Visual Studio).
4. Expand the **Type information** region.
5. Add the **IsBinding** property to the initializer of the new **ObjectTypeInfo** object and set the value to _true_. See [Setting the TypeInfo for binding classes](#setting-the-typeinfo-for-binding-classes) for details.

   > **Info:** **Note**: On web application installations, you need to manually include the _Info_ and _InfoProvider_ class files into the **CMSApp\_AppCode** project and build the solution.
6. Manually set the class's ID fields as foreign keys in your database. See [Create Foreign Key Relationships](http://msdn.microsoft.com/en-us/library/ms189049.aspx) for more information.

The binding class is now ready. You can create relationships between objects using the API or prepare a user interface for this purpose. See the [Example](#example---creating-a-binding-class) section to learn more.

### Compound primary key

Use the following steps to create a binding class without its own identity column:

1. Open the **Modules** application and edit the custom module where you want to create the binding class.
2. Select the **Classes** tab and click **New class**.
3. Fill in the **Class display name** and **Class** identifier.
4. Click **Next**.
5. Enter the **Primary key name**. We recommend using the name of the identifier column of the first class in the relationship.
6. Enable **Is M:N table**.
7. Click **Next**.
8. Set the following options for the default primary key field:

   - **Reference to**: select the first class in the relationship
   - **Reference type**: Binding
9. Click **New field** to create _one or more_ additional fields for storing the IDs of the related objects:

   - **Field type**: Primary key (use the _Primary key_ field type for all of the ID fields in Kentico — the result in the database is a compound primary key)
   - **(General) Field type**: Integer number
   - **Required**: yes (checked)
   - **Reference to**: select the appropriate class
   - **Reference type**: Binding
   - **Display field in the editing form**: no (not checked)
10. Click **Save** for each field and then **Next**.
11. Click **Finish**.

The system creates the corresponding table in the database. Perform the following steps to prepare the class's code and finalize the database table:

1. Select the **Code** tab in the editing interface of the binding class.
2. Click **Save code**. The system generates an _Info_ and _InfoProvider_ class for the binding object.
3. Edit the _Info_ class (for example in Visual Studio).
4. Expand the **Type information** region.
5. Set the **idColumn** parameter to _null_ in the **ObjectTypeInfo** constructor (the fourth parameter).
6. Add the **IsBinding** property to the initializer of the new **ObjectTypeInfo** object and set the value to _true_. See [Setting the TypeInfo for binding classes](#setting-the-typeinfo-for-binding-classes) for details.

   > **Info:** **Note**: On web application installations, you need to manually include the _Info_ and _InfoProvider_ class files into the **CMSApp\_AppCode** project and build the solution.
7. Manually set the class's ID fields as foreign keys in your database. See [Create Foreign Key Relationships](http://msdn.microsoft.com/en-us/library/ms189049.aspx) for more information.

The binding class is now ready. You can create relationships between objects using the API or prepare a user interface for this purpose. See the [Example](#example---creating-a-binding-class) section to learn more.

## Setting the TypeInfo for binding classes

The **TypeInfo** is code that defines the general behavior and basic properties of classes in Kentico. You can configure the TypeInfo inside the _Info_ class of a given Kentico class using an object of the **ObjectTypeInfo** type.

See the sections below to learn how to set the TypeInfo for binding classes.

> **Info:** **Note**: When you generate the _Info_ class from the interface of the **Modules** application and have the fields set correctly for the binding class, the system configures _most_ of the TypeInfo automatically.

**Parameters of the ObjectTypeInfo constructor**:

- **idColumn (4)** - the name of the identity column of the binding class. Must be _null_ for binding classes that do not have a dedicated identity column (with a compound primary key).
- **siteIDColumn (10)** - for bindings to site objects, must contain the name of the class column that stores the ID of the related site. Set to _null_ for bindings between non-site objects\*.\*
- **parentID (11)** - the name of the column that stores the ID of the first class in the relationship.
- **parentObjectType (12)** - the object type name of the first class in the relationship. You can get the value from the OBJECT\_TYPE constant in the given class's _Info_ class.

**Properties in the ObjectTypeInfo initializer**:

- **ModuleName** - the code name of the module that contains the binding class.
- **IsBinding** - _always set to _true_ for binding classes_.\*\*
- **DependsOn** - List of **ObjectDependency** objects representing the classes in the relationship. Add an ObjectDependency for each class in the relationship except for the one specified via the _parent_ parameters in the constructor. Not required for site bindings.

```csharp title="Examples"

// Sample TypeInfo definition for a general binding class
// Relationship between custom offices and roles
public static ObjectTypeInfo TYPEINFO = new ObjectTypeInfo(typeof(OfficeRoleInfoProvider), OBJECT_TYPE, "CompanyOverview.OfficeRole", "OfficeRoleID", null, null, null, null, null, null, "OfficeID", "companyoverview.office")
{
    ModuleName = "CompanyOverview",
    IsBinding = true,
    DependsOn = new List<ObjectDependency>()
    {
        new ObjectDependency("RoleID", "cms.role", ObjectDependencyEnum.Binding),
    },
};

// Sample TypeInfo definition for a site binding class
// Relationship between custom offices and sites
public static ObjectTypeInfo TYPEINFO = new ObjectTypeInfo(typeof(OfficeSiteInfoProvider), OBJECT_TYPE, "CompanyOverview.OfficeSite", "OfficeSiteID", null, null, null, null, null, "SiteID", "OfficeID", "companyoverview.office")
{
    ModuleName = "CompanyOverview",
    IsBinding = true
};

```

## Example - Creating a binding class

The following example demonstrates how to create a binding class, including an editing interface. The sample binding class allows the creation of relationships between offices and users. Each relationship indicates that a user is a manager of a given office.

> **Note:** To follow the example, you first need to create the **Company overview** custom module according to the instructions in [Creating custom modules](https://docs.kentico.com/k8/custom-development/creating-custom-modules.md).

### Preparing the binding class

1. Open the **Modules** application and edit the **Company overview** module.
2. Select the **Classes** tab and click **New class**.
3. Fill in the class names:
   - **Class display name**: Office manager binding
   - **Class**: OfficeUser
4. Click **Next**.
5. In step 2, leave the default values and click **Next**.
6. Create two fields for storing the IDs of the related offices and users. Click **New field**, set the properties, and click **Save** for each field:

   - **Field type**: Standard field
   - **Field name**: OfficeID
   - **(General) Field type**: Integer number
   - **Required**: yes (checked)
   - **Reference to**: Custom office
   - **Reference type**: Binding
   - **Display field in the editing form**: no (not checked)
   - **Field type**: Standard field
   - **Field name**: UserID
   - **(General) Field type**: Integer number
   - **Required**: yes (checked)
   - **Reference to**: User
   - **Reference type**: Binding
   - **Display field in the editing form**: no (not checked)
7. Click **Next**.
8. Click **Finish**.

Generate the code required for the binding class's API (including the [TypeInfo](#setting-the-typeinfo-for-binding-classes)):

1. Select the **Code** tab in the editing interface of the _Office manager binding_ class.
2. Click **Save code**. The system generates an _Info_ and _InfoProvider_ class for the binding object in the _\~/App\_Code/CMSModules/CompanyOverview_ folder.
3. Open your web project in Visual Studio and edit _**OfficeUserInfo.cs**_.

   > **Note:** **Note**: On web application installations, the system generates the files in the **Old\_App\_Code** folder. You need to manually include the files into the **CMSApp\_AppCode** project and build the solution.
4. Expand the **Type information** region.
5. Add the **IsBinding** property to the initializer of the new **ObjectTypeInfo** object and set the value to _true_:

   ```csharp

   public static ObjectTypeInfo TYPEINFO = new ObjectTypeInfo(typeof(OfficeUserInfoProvider), OBJECT_TYPE, "CompanyOverview.OfficeUser", "OfficeUserID", null, null, null, null, null, null, "OfficeID", "companyoverview.office")
   {
       ModuleName = "CompanyOverview",
       IsBinding = true,
       DependsOn = new List<ObjectDependency>() 
       {
           new ObjectDependency("UserID", "cms.user", ObjectDependencyEnum.Binding), 
       },
   };

   ```
6. Save the change (build the project on web application installations).

Finally, create a [resource string](https://docs.kentico.com/k8/multilingual-websites/setting-up-a-multilingual-user-interface/working-with-resource-strings.md) for displaying the binding class's object type name:

1. In the Kentico administration interface, open the **Localization** application.
2. On the **Resource strings** tab, click **New string**.
3. Enter the following **Key**: _ObjectType.CompanyOverview\_OfficeUser_ (the general format is _ObjectType._)
4. Type the following text for the English version of the key: _Office manager binding_
5. Click **Save**.

The system uses the resource string in the administration interface, for example when selecting classes.

### Creating foreign keys for the database table

You need to manually set the ID columns of your custom binding classes as foreign keys in the corresponding database table.

In this example, create foreign keys for the **OfficeID** and **UserID** columns in the **CompanyOverview\_OfficeUser** table. Add relationships with the corresponding columns in the **CompanyOverview\_Office** and **CMS\_User** tables respectively.

You can either use SQL Server Management Studio or execute an SQL script. See [Create Foreign Key Relationships](http://msdn.microsoft.com/en-us/library/ms189049.aspx) for more information.

### Building a binding management interface

The following steps show how to create a custom page in the administration interface that allows users to set relationships between objects:

1. In the **Modules** application, edit the **Company overview** module.
2. Select the **User interface** tab.
3. Expand the **CMS -> Administration -> Custom** element in the UI element tree.

#### Adding tabs to the office editing interface:

1. Select **Company overview** in the UI element tree.
2. Click **New element** ().
3. Set the following properties for the element:

   - **Display name**: Edit office tabs
   - **Code name**: EditOfficeTabs (**Important**: The code name of elements for editing objects under listings must always start with the _**Edit**_ keyword)
   - **Module**: Company overview
   - **Page template**: Vertical tabs
4. Click **Save**.
5. Switch to the **Properties** tab, expand the **Breadcrumbs** section and enable **Display breadcrumbs**.
6. Click **Save**.

#### Moving the original office editing element under the tabs:

1. Select the **Edit office** element (from the example in [Creating custom modules](https://docs.kentico.com/k8/custom-development/creating-custom-modules.md)).
2. Change the element's names and move it under the new tabs element:
   - **Display name**: General
   - **Code name**: GeneralEditOffice
   - **Parent element**: Edit office tabs
3. Click **Save**.
4. Open the **Properties** tab and disable **Display breadcrumbs** (if necessary).
5. Click **Save**.

#### Adding the binding management element:

1. Select the **Edit office tabs** element in the tree.
2. Click **New element** ().
3. Set the following properties for the element:

   - **Display name**: Managers
   - **Code name**: ManagersEditOffice
   - **Module**: Company overview
   - **Page template**: Edit bindings
4. Click **Save**.
5. Switch to the **Properties** tab and set the following values in the **Binding** category:

   - **Binding object type**: Office manager binding
   - **Target object type**: User
   - **Where condition**: OfficeID = {% UIContext.ObjectID %}

     > **Info:** The following properties define the **Office – User** binding:
     >
     > - **Object type** - the first class in the relationship (in this case, the element inherits the _**Custom office**_ object type from the parent elements)
     > - **Binding object type** - the binding class itself (_**Office manager binding**_)
     > - **Target object type** - the second class in the relationship _(**User**_ in this case)The **Where condition** ensures that only the relationships of the currently edited office object are displayed.
6. Click **Save**.

The binding editing interface is now ready.

![Defining a UI element for binding management](https://docs.kentico.com/docsassets/k8/creating-custom-binding-classes/Edit_Bindings_Element.png "Defining a UI element for binding management")

If you open the **Company overview** application in the **Custom** category and edit an office, you can manage the office-user bindings on the **Managers** tab.

![Editing the manager relationships between offices and users](https://docs.kentico.com/docsassets/k8/creating-custom-binding-classes/Binding_Management.png "Editing the manager relationships between offices and users")