Question

任何正文都可以将以下c＃代码翻译为vb。我已经尝试了telarik代码转换器，但我在expression.call遇到问题，它根本不会编译。

private static IOrderedQueryable<T> OrderingHelper<T>(IQueryable<T> source, string propertyName, bool descending, bool anotherLevel)
{
    ParameterExpression param = Expression.Parameter(typeof(T), string.Empty);
    MemberExpression property = Expression.PropertyOrField(param, propertyName);
    LambdaExpression sort = Expression.Lambda(property, param);

    MethodCallExpression call = Expression.Call(    
        typeof(Queryable),
        (!anotherLevel ? "OrderBy" : "ThenBy") + (descending ? "Descending" : string.Empty),
        new[] { typeof(T), property.Type }, // error line
        source.Expression,
        Expression.Quote(sort));

    return (IOrderedQueryable<T>)source.Provider.CreateQuery<T>(call);
}

感谢 Thurein

Answer 1

Function foo(Of T)(ByVal source As IQueryable(Of T), ByVal propertyName As String, ByVal descending As Boolean, ByVal anotherLevel As Boolean) As Object
    Dim param = Expression.Parameter(GetType(T), String.Empty)
    Dim [property] = Expression.PropertyOrField(param, propertyName)
    Dim sort = Expression.Lambda([property], param)

    Dim [call] = Expression.Call(
     GetType(Queryable),
     If(Not anotherLevel, "OrderBy", "ThenBy") & If(descending, "Descending", String.Empty),
     New Type() {GetType(T), [property].Type},
     source.Expression,
     Expression.Quote(sort))

    Return CType(source.Provider.CreateQuery(Of T)([call]), IOrderedQueryable(Of T))

End Function

在vb.net中的linq表达式

1 个答案: