MetaField class

A MetaField object represent a meta class field. Fields represent information that an object contains. Fields are like variables because they can be directly read or set. For example, if you have an object named "Car", you could store its color in a field named "Color".

From the MetaField object you can get complete information about fields:

• Name
• Meta Type
• Default Value
• Formula for auto-calculated columns
• Is Nullable
• Is ReadOnly
• Is Primary Key

Getting a meta field collection

The collection of meta fields is available from the MetaClass.Fields property, and it will return a MetaFieldCollection object.

Example: The following example writes all fields to trace

foreach (MetaField field in mc.Fields)
{
 System.Diagnostics.Trace.WriteLine(field.Name);
}

Creating a meta field

Call the CreateMetaField method of the MetaClass class, passing name, friendly name, type, is nullable flag, default value and attributes to create a new meta field. The attributes depends on the meta type.

Example: Create a new Guid meta field

public MetaField CreateGuid(string name, string friendlyName, bool isNullable)
{
if (name == null)
throw new ArgumentNullException("name");
if (friendlyName == null)
throw new ArgumentNullException("friendlyName");
AttributeCollection attr = new AttributeCollection();
string defaultValue = isNullable ? string.Empty : "newid()";
MetaField retVal = this.MetaClass.CreateMetaField(name, friendlyName, MetaFieldType.Guid, isNullable, defaultValue, attr);
return retVal;
}

Deleting a meta field

Call the CreateMetaField method of the MetaClass class, passing name, friendly name, type, is nullable flag, default value and attributes to create a new meta field. The attributes depends on the meta type.

Example: Create a new Guid meta field

public MetaField CreateGuid(string name, string friendlyName, bool isNullable)
{
if (name == null)
throw new ArgumentNullException("name");
if (friendlyName == null)
throw new ArgumentNullException("friendlyName");
AttributeCollection attr = new AttributeCollection();
string defaultValue = isNullable ? string.Empty : "newid()";
MetaField retVal = this.MetaClass.CreateMetaField(name, friendlyName, MetaFieldType.Guid, isNullable, defaultValue, attr);
return retVal;
}

Deleting a meta field

Call the DeleteMetaField method of the MetaClass class, passing the meta field object to, delete a field from the meta class.

Example: Find column by name and drop

// Delete field
mc. DeleteMetaField(mc.Fields\["Book Title"]);