--- title: MetaClass class slug: commerce-connect-15/docs/metaclass-class docTags: createdAt: 2026-07-30T20:34:41.000Z --- Fields represent information that an object contains. Fields are like variables because they can be read or set directly. For example, if you have an object named *Car*, you can store its color in a field named *Color*. :::hint{type="info"} **Note** `MetaClass` has an optional `TitleFieldName` property that specifies the name of title field. Be careful to define `TitleFieldName` with a correct string field name if you want to create a reference to this meta-class. ::: You can use meta-class to create an entity object, and modify meta-class fields (add, remove) at runtime. When you create and delete meta-classes, remember that you can modify a meta-model only in **Design** mode. See the [MetaClassManager](https://world.optimizely.com/documentation/developer-guides/commerce/business-foundation/business-meta-model/MetaClassManager-class/) class section. ## Get a MetaClass collection The table collection is available from the `MetaClassManager.MetaClasses` property and it returns a `MetaClassCollection` object. The following example writes only user tables to trace. ```csharp // Get MetaModel MetaClassManager metaModel = DataContext.Current.MetaModel; // Step 3. Enum meta-classes foreach (MetaClass mc in metaModel.MetaClasses) { Trace.WriteLine(mc.Name); } ``` ## Delete a meta-class Call the `DeleteMetaClass` method of the `MetaClassManager` class, passing the meta-class object to delete a meta-class. The method removes a meta-class definition and data, references, and permission specifications for that meta-class. **Example:** Find meta-class by name and delete: ```csharp // Open Meta-model edit scope using (MetaClassManagerEditScope scope = DataContext.Current.MetaModel.BeginEdit()) { // Find table MetaClass mc = DataContext.Current.MetaModel.MetaClasses ["Class_1"]; // Drop table DataContext.Current.MetaModel.DeleteMetaClass (table); // Save Changes scope.SaveChanges(); } ``` ## MetaClass Card extension You can extend `MetaClass` with Cards. To do this, you create a `Card `field in the meta-class, saving the current card's reference. Call the `CreateCardField` method of the `MetaClass` to create a `Card` field. Each card can have its own field set, but only one can be active in the entity object. You can create a `Card` meta-class if a meta-class has a card field. The `Card` meta-class is visible in a collection of meta-classes like the original meta-class but will have an `IsCard` property with the value `true`. You can add meta-fields or delete card meta-classes and common meta-classes. - Call the `CardOwner` property of `MetaClass` to get the card owner for the current card. - Call the `SupportsCards` property of the `MetaClass` class to specify whether the meta-class supports cards. - Call the `GetMetaClassSupportedCard` of the `MetaClassManager` class to get a collection of meta-classes supporting cards. To start work with the card, create an entity object passing the current card meta-class name to the card field, and all card fields are available in the current entity object. When you save the object, it saves the original common fields, the current card type, and the current card field. Card fields are loaded automatically and are available in the filter expressions. The following example creates a `Client` meta-class, marks that meta-class supports cards, and creates three cards with field sets: *Regional Client*, *Foreign Client*, and *Partner*. If you create a new client object without cards, only meta-class fields are available. But if you set the card property, the fields from the card are available in the entity object automatically. ![](https://api.archbee.com/api/optimize/BrbvVORKJ5iIeSMZye5kI/hAKDKzeM_YUVSJj09Uryr-20260723-164629.png "bfbmm1.png") ## Validators Meta-class supports validation. The `Validator` ensures that a meta-class is configured properly. `Validators` are instantiated during runtime when you save the entity object. If a meta-class is not properly configured, the validator throws an exception for the incorrect values. By default, meta-fields add validators to meta-classes. For example, the email field adds an email validator to check that email property has the correct email, text field, and add maximum length validators. Call the `Validators` property of the `MetaClass` class to get a collection of validators for the current class. You can create custom validators by creating a class that implements the `IValidator`, and implements `ErrorMessage`, the `IsValid` property, and the `Validate` method. Then, you can add a validator to the collection of validators for the current class. If you develop a custom meta-type, you should add your validators in `AssignValidators` and remove them in the `RemoveValidators` methods of the meta field installer. **Example:** `CurrencyFieldValidator` ```csharp using System; using System.Collections.Generic; using System.Text; using System.Text.RegularExpressions; using System.Reflection; using System.Globalization; namespace Mediachase.BusinessFoundation.Data { /// /// Represents a currency field validator. /// public class CurrencyFieldValidator: BaseFieldValidator { private bool _allowNull = true; public CurrencyFieldValidator() {} public bool AllowNull { get { return _allowNull; } set { _allowNull = value; } } protected override bool EvaluateIsValid() { object fieldValue = base.GetValue(); // Check Null if (fieldValue == null && !this.AllowNull) { base.ErrorMessage = string.Format(CultureInfo.InvariantCulture, "The '{0}' field doesn't allow null.", this.FieldName); return false; } if (fieldValue == null) return true; // Check Type if (fieldValue.GetType() != typeof (Decimal)) { base.ErrorMessage = string.Format(CultureInfo.InvariantCulture, "Wrong type '{1}'. '{0}' field expects decimal.", this.FieldName, fieldValue.GetType().GetType()); return false; } return true; } } } ```