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

Returns the only element of a sequence that satisfies a specified condition, or the appropriate NullEntity if no such element exists; this method throws an exception if more than one element satisfies the condition.

Syntax

Visual Basic
C#

'Declaration
 
<ExtensionAttribute()>
Public Overloads Shared Function SingleOrNullEntity(Of TSource)( _
   ByVal source As IEntityScalarQuery(Of TSource), _
   ByVal predicate As Expression(Of Func(Of TSource,Boolean)), _
   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 predicate As Expression(Of Func(Of TSource,Boolean))
Dim userCallback As Action(Of EntityScalarQueryOperation(Of TSource))
Dim userState As Object
Dim value As EntityScalarQueryOperation(Of TSource)
 
value = EntityScalarQueryAsyncExtensions.SingleOrNullEntity(Of TSource)(source, predicate, userCallback, userState)

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

Parameters

source
predicate
userCallback
userState

Type Parameters

TSource

Example

public void AsyncSingleOrNullEntityWithPredicate() {
   var op = _entityManager.Employees.AsScalarAsync().SingleOrNullEntity(e => e.Id == 1);
   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