SingleOrNullEntity<TSource>(IEntityScalarQuery<TSource>,Action<EntityScalarQueryOperation<TSource>>,Object) Method

Returns the only element of a sequence, or the appropriate NullEntity if the sequence is empty; this method throws an exception if there is more than one element in the sequence.

Syntax

Visual Basic
C#

'Declaration
 
<ExtensionAttribute()>
Public Overloads Shared Function SingleOrNullEntity(Of TSource)( _
   ByVal source As IEntityScalarQuery(Of TSource), _
   ByVal userCallback As Action(Of EntityScalarQueryOperation(Of TSource)), _
   Optional ByVal userState As Object _
) As EntityScalarQueryOperation(Of TSource)

'Usage
 
Dim source As IEntityScalarQuery(Of TSource)
Dim userCallback As Action(Of EntityScalarQueryOperation(Of TSource))
Dim userState As Object
Dim value As EntityScalarQueryOperation(Of TSource)
 
value = EntityScalarQueryAsyncExtensions.SingleOrNullEntity(Of TSource)(source, userCallback, userState)

[Extension()]
public static EntityScalarQueryOperation<TSource> SingleOrNullEntity<TSource>( 
   IEntityScalarQuery<TSource> source,
   Action<EntityScalarQueryOperation<TSource>> userCallback,
   object userState
)

Parameters

source
userCallback
userState

Type Parameters

TSource

Example

public void AsyncSingleOrNullEntity() {
  var op = _entityManager.Employees.Where(e => e.Id == 1).AsScalarAsync().SingleOrNullEntity();
  op.Completed += (o, e) => {
    var emp = e.Result;
  };
}

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

EntityScalarQueryAsyncExtensions Class
EntityScalarQueryAsyncExtensions Members
Overload List