QueryableFilterUserControl.GetQueryable(IQueryable) 方法

定义

命名空间:

System.Web.DynamicData

程序集:

System.Web.DynamicData.dll

从源IQueryable对象获取转换IQueryable的对象。

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

参数

source

IQueryable

源 IQueryable 对象。

返回

IQueryable

源对象中的IQueryable转换IQueryable对象。

示例

此方法实现将源 IQueryable 对象转换为目标 IQueryable 对象。 你可能希望实现的 IQueryable 表达式示例包括按顺序、范围或搜索。

下面的示例演示如何实现 GetQueryable 派生自 QueryableFilterUserControl的布尔筛选器的方法。

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

注解

如果从 QueryableFilterUserControl中派生控件，则必须实现此方法。