Delete Relation using condition¶

The API deletes objects from a relationship with their parent. The objects are identified implicitly through a whereClause condition.

Blocking API¶

Using Dictionary

int result = Backendless.Data.Of( "TABLE-NAME" ).DeleteRelation( 
                               Dictionary<string, object> parentObject,
                               string relationColumnName,
                               string whereClause );

Custom Class

int result = Backendless.Data.Of<E>().DeleteRelation( 
                              E parentObject,
                              string relationColumnName,
                              string whereClause );

Non-Blocking API¶

Using Dictionary

Backendless.Data.Of( "TABLE-NAME" ).DeleteRelation( 
                  Dictionary<string, object> parentObject,
                  string relationColumnName,
                  string whereClause,
                  AsyncCallback<int> callback );

Custom Class

Backendless.Data.Of<E>().DeleteRelation( 
                 E parentObject,
                 string relationColumnName,
                 string whereClause,
                 AsyncCallback;<int> callback );

where:

Argument	Description
`TABLE-NAME`	Name of the table where the parent object is stored.
`E`	.NET class of the parent object. The class name identifies the table where the parent object is stored.
`parentObject`	The object for which the relation with the identified children will be deleted. When this argument is an instance of `Dictionary<string, object>` (for the dictionary-based approach), it must contain the `"objectId"` property.
`relationColumnName`	Name of the column representing the relation. Relationship between the child objects identified by `whereClause` will be deleted for this column in `parentObject`.
`whereClause`	a where clause condition identifying the objects in the child table which will be removed from the relation to the parent object.
`callback`	a responder object which will receive a callback when the relation has been deleted or if an error occurs. Applies to the asynchronous method only.

Return Value¶

Number of child objects removed from the relationship. The asynchronous call receives the return value through a callback executed on the AsyncCallback object.

Example¶

The following example deletes a relation between a Person object and all the related objects in the related table identified by column "user" which match the provided query:

name='Joe' or name = 'Frank'

As a result of the operation, all related objects where the name property is either Joe or Frank will be deleted from the relation.

Using Dictionary

Dictionary<string, object> parentObject = new Dictionary<string, object>();
parentObject[ "objectId" ] = "41230622-DC4D-204F-FF5A-F893A0324800";

AsyncCallback<int> deleteRelationCallback = new AsyncCallback<int>(
  howMany =>
  {
    System.Console.WriteLine( String.Format( "Server has removed {0} objects from the relation", howMany ) );
  },
  error =>
  {
    System.Console.WriteLine( "Server returned an error " + error.Message );
  } );

Backendless.Data.Of( "Person" ).DeleteRelation( parentObject, 
                  "user", 
                  "name = \"Joe\" or name = \"Frank\"", 
                  deleteRelationCallback );

Custom Class

Person personObject = // personObject retrieval is out of scope in this example

AsyncCallback<int> deleteRelationCallback = new AsyncCallback<int>(
  howMany =>
  {
    System.Console.WriteLine( String.Format( "Server has removed {0} objects from the relation", howMany ) );
  },
  error =>
  {
    System.Console.WriteLine( "Server returned an error " + error.Message );
  } );

Backendless.Data.Of<Person>().DeleteRelation( 
                  personObject, 
                  "user", 
                  "name = \"Joe\" or name = \"Frank\"",
                  deleteRelationCallback );