QueryableFilterUserControl.GetQueryable(IQueryable) 方法

public:
 abstract System::Linq::IQueryable ^ GetQueryable(System::Linq::IQueryable ^ source);

public abstract System.Linq.IQueryable GetQueryable (System.Linq.IQueryable source);

abstract member GetQueryable : System.Linq.IQueryable -> System.Linq.IQueryable

Public MustOverride Function GetQueryable (source As IQueryable) As IQueryable

參數

傳回

來自來源 IQueryable 物件的已轉換 IQueryable 物件。

範例

這個方法會實作，以將來源 IQueryable 物件轉換成目標 IQueryable 物件。 您可能想要實作的 IQueryable 運算式範例包括依、範圍或搜尋的順序。

下列範例示範如何針對 GetQueryable 衍生自 QueryableFilterUserControl 的布林篩選實作 方法。

public override IQueryable GetQueryable(IQueryable source) {  
    if (String.IsNullOrEmpty(DropDownList1.SelectedValue)) {  
        return source;  
    }  

    bool value = Convert.ToBoolean(DropDownList1.SelectedValue);  

    ParameterExpression parameterExpression =   
        Expression.Parameter(source.ElementType, "item");  
    Expression body = BuildQueryBody(  
        parameterExpression, value);  

    LambdaExpression lambda = Expression.Lambda(body,   
        parameterExpression);  
    MethodCallExpression whereCall = Expression.Call(  
        typeof(Queryable),   
        "Where",   
        new Type[] { source.ElementType },   
        source.Expression, Expression.Quote(lambda));  
    return source.Provider.CreateQuery(whereCall);  
}  

Public Overloads Overrides Function GetQueryable(ByVal source As IQueryable) As IQueryable   
    If [String].IsNullOrEmpty(DropDownList1.SelectedValue) Then   
        Return source   
    End If   

    Dim value As Boolean = Convert.ToBoolean(DropDownList1.SelectedValue)   

    Dim parameterExpression As ParameterExpression = Expression.Parameter(source.ElementType, "item")   
    Dim body As Expression = BuildQueryBody(parameterExpression, value)   

    Dim lambda As LambdaExpression = Expression.Lambda(body, parameterExpression)   
    Dim whereCall As MethodCallExpression = Expression.[Call](GetType(Queryable), "Where", _  
         New Type() {source.ElementType}, source.Expression, Expression.Quote(lambda))   
    Return source.Provider.CreateQuery(whereCall)   
End Function  

備註

如果您從 QueryableFilterUserControl 衍生控制項，則必須實作這個方法。

適用於