从多个参数组合Linq到实体查询 [英] Composing Linq to Entity Query from multiple parameters
问题描述
基本上我有可以选择的用户1 *项目列表控件。
我不能包围的部分是以下内容:
我如何动态构建一个 Where AND(field等于该OR字段等于此OR ...)子句
其中项目数是变体。
数据库域字段示例内容:'26,21,22,100,164,130'
示例:(想法是能够根据所选项目的数量生成这个数据)
Offre.Where(o => o.Domain.Contains 26)|| o.Domain.Contains(100))
Offre.Where(o => o.Domain.Contains(26))
Offre.Where(o => o.Domain.Contains(26)|| o.Domain.Contains(100)|| o.Domain.Contains(22))
然后我可以轻松地将生成的查询作为IQueryable,并添加到此对象以构建我的查询。
有人可以指出我的AND(OR .. OR)子句的正确方向吗?
C# / p>
static Expression< Func< TElement,bool>> BuildContainsExpression< TElement,TValue>(
表达式< Func< TElement,TValue>> valueSelector,IEnumerable< TValue>值)
{
if(null == valueSelector){throw new ArgumentNullException(valueSelector); }
if(null == values){throw new ArgumentNullException(values); }
ParameterExpression p = valueSelector.Parameters.Single();
// p => valueSelector(p)== values [0] || valueSelector(p)== ...
if(!values.Any())
{
return e =>假;
}
var equals = values.Select(value =>(Expression)Expression.Equal(valueSelector.Body,Expression.Constant(value,typeof(TValue)) ));
var body = equals.Aggregate< Expression>((accumulate,equal)=> Expression.Or(accumulate,equal));
return Expression.Lambda
}
使用此实用程序方法,
var query2 = context.Entities.Where(BuildContainsExpression< Entity,int>(e => e.ID,ids));
VB.Net
$ b $公共共享函数BuildContainsExpression(对于TElement,TValue)(_
ByVal valueSelector As Expression(Of Func(Of TElement,TValue)),_
ByVal值作为IEnumerable(Of TValue)_
)As Expression(Of Func(Of TElement,Boolean))
'validate arguments
如果IsNothing(valueSelector)然后抛出新的ArgumentNullException( valueSelector)
如果IsNothing(值)然后抛出新的ArgumentNullException(values)
Dim p As ParameterExpression = valueSelector.Parameters.Single()
如果不是值。任何然后
返回_
函数(e)False
结束如果
Dim equals = values.Select(_
函数(v)_
Expression.Equal(valueSelector.Body,Expression.Constant(v,GetType(TValue)))_
)
Dim body = equals.Aggregate(_
Function积累,相等)_
Expression.Or(accumulate,equal)_
)
返回Expression.Lambda(Of func(Of TElement,Boolean))(body,p)
End Function
使用此实用程序
Dim query = m_data。提供
如果(selectedSectors.Count> 0)然后
query = query.Where(BuildContainsExpression(Function(o As Offer)o.Value,selectedSectors))
End If
I'm currently building a detailed search and I am trying to figure out how to compose my Linq query to my Entity.
basically I have users that can select 1* items in a list control. the part I can't wrap my head around is the following:
how can I dynamically build a Where AND( field is equal to this OR field is equal to this OR...) clause where the number of items is variant.
database Domain Field sample content : '26, 21, 22, 100, 164, 130'
Example: (The idea is to be able to generate this depending on the number of items selected)
Offre.Where(o=> o.Domain.Contains("26") || o.Domain.Contains("100") )
Offre.Where(o=> o.Domain.Contains("26") )
Offre.Where(o=> o.Domain.Contains("26") || o.Domain.Contains("100") || o.Domain.Contains("22") )
then I can easily have the resulting query as an IQueryable and add on to this object to build my query.
can someone point me inthe right direction for my AND ( OR .. OR ) clause ?
To work around this restriction, you can manually construct an expression (Source)
C#
static Expression<Func<TElement, bool>> BuildContainsExpression<TElement, TValue>(
Expression<Func<TElement, TValue>> valueSelector, IEnumerable<TValue> values)
{
if (null == valueSelector) { throw new ArgumentNullException("valueSelector"); }
if (null == values) { throw new ArgumentNullException("values"); }
ParameterExpression p = valueSelector.Parameters.Single();
// p => valueSelector(p) == values[0] || valueSelector(p) == ...
if (!values.Any())
{
return e => false;
}
var equals = values.Select(value => (Expression)Expression.Equal(valueSelector.Body, Expression.Constant(value, typeof(TValue))));
var body = equals.Aggregate<Expression>((accumulate, equal) => Expression.Or(accumulate, equal));
return Expression.Lambda<Func<TElement, bool>>(body, p);
}
Using this utility method,
var query2 = context.Entities.Where(BuildContainsExpression<Entity, int>(e => e.ID, ids));
VB.Net
Public Shared Function BuildContainsExpression(Of TElement, TValue)( _
ByVal valueSelector As Expression(Of Func(Of TElement, TValue)), _
ByVal values As IEnumerable(Of TValue) _
) As Expression(Of Func(Of TElement, Boolean))
' validate arguments
If IsNothing(valueSelector) Then Throw New ArgumentNullException("valueSelector")
If IsNothing(values) Then Throw New ArgumentNullException("values")
Dim p As ParameterExpression = valueSelector.Parameters.Single()
If Not values.Any Then
Return _
Function(e) False
End If
Dim equals = values.Select( _
Function(v) _
Expression.Equal(valueSelector.Body, Expression.Constant(v, GetType(TValue))) _
)
Dim body = equals.Aggregate( _
Function(accumulate, equal) _
Expression.Or(accumulate, equal) _
)
Return Expression.Lambda(Of Func(Of TElement, Boolean))(body, p)
End Function
Using this utility method
Dim query = m_data. Offer
If (selectedSectors.Count > 0) Then
query = query.Where(BuildContainsExpression(Function(o As Offer) o.Value, selectedSectors))
End If
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