动态Linq查询 [英] Dynamic Linq Query

问题描述

我有一个返回List< Dictionary< string，object>>的函数。



此列表的示例如下所示



{（"Source"，"srchostname1"），（"Destination"，"destination"），（"State"， ），（"Created"，01/02/2010 12:32:20 pm），（"Source"，"srchostname2"），（"Destination"，"destination2"），（"State"， "错误"），（"创建"，02/02/2010 12:32:20 pm），（"Source"，"srchostname3"），
（"Destination"，"destination3"和），（"状态"，"错误"），（"创建"，04/02/2010 12:32:20 pm）}




此列表将包含-1000个此类条目。



我希望能够根据"来源"进行过滤。 "目的地" "状态" "创建" ;.此过滤器基于用户的选择。它可以是上述任何一种的组合。我也希望能够通过以上任何一种方式进行订购。我也想要
能够"排序"根据用户的选择升序或降序。我还想在结果集上使用Paging。



如何使用动态linq查询来实现上述目标。我正在谷歌搜索，我看到一些PredicateBuilder类可用于过滤器（where子句）  part。谁能帮助我如何使用PredicateBuilder类或任何其他方式实现上述目的。

解决方案

//要查询的数据

List< Dictionary< string，object>> listOfStuff = new List< Dictionary< string，object>>（）

{  新词典< string，object> {{" Source"，" srchostname1"}，{" Destination"，" destination"}，{" State"，" Transferring"}，{" Created"，DateTime.Parse（" 01 / 02/2010 12:32:20 pm"）}}，

   新词典< string，object> {{" Source"，" srchostname2"}，{" Destination"，" destination2"}，{" State"，" Error"}，{" Created"，DateTime.Parse（" 02） / 02/2010 12:32:20 pm"）}}，

   新词典< string，object> {{" Source"，" srchostname3"}，{" Destination"，" destination3"}，{" State"，" Error"}，{" Created"，DateTime.Parse（" 04） / 02/2010 12:32:20 pm"）}}

};

//要应用的过滤器：名称和值...

List< Tuple< string，object>> filters = new List< Tuple< string，object>>（）

{

    new Tuple< string，object>（" Source"，" srchostname1"），

    new Tuple< string，object>（" State"，" Transferring"）

};

// sort order arguments：field name，ordinal（在sort args）中，升序（false）或降序（true）

List< Tuple< string，int，bool>> sortArguments = new List< Tuple< string，int，bool>>

{

    new Tuple< string，int，bool>（" Source"，1，false），

    new Tuple< string，int，bool>（" Destination"，2，true）

};

//将列表转换为查询

var query = listOfStuff.AsQueryable（）;
$


//应用过滤器

foreach（元组< string，object> ;过滤器过滤器）

{

    string fieldName = filter.Item1;

    object fieldValue = filter.Item2;

    query = query.Where（d => d.Any（v => v.Key == fieldName&& v.Value == fieldValue））;

}

//应用排序参数（按降序排列）

foreach（sortArguments.OrderByDescending（o => o.Item2）中的元组< string，int，bool> sortArg）

{

     string orderByCol = sortArg.Item1;

     bool  descendingOrder = sortArg.Item3;



    if（descendingOrder == false）

    {

        query = query.OrderBy（o => o [orderByCol]）;

    }
   否则为
    {

        query = query.OrderByDescending（o => o [orderByCol]）;

    }
}

//执行查询并将结果转换为列表

var result = query.ToList（）;

I have a function which returns a List<Dictionary<string, object>>.

An example of this list would look like this

{ ("Source", "srchostname1"), ("Destination", "destination"), ("State","Transferring"), ("Created",01/02/2010 12:32:20pm) , ("Source", "srchostname2"), ("Destination", "destination2"), ("State","Error"), ("Created",02/02/2010 12:32:20pm), ("Source", "srchostname3"), ("Destination", "destination3"), ("State","Error"), ("Created",04/02/2010 12:32:20pm) }

This list would contains -1000- of such entries.

I would like to be able filter based on "Source" "Destination" "State" "Created". This filter is based on user's choice. It can be a combination of any of the above. I would also like to be able to orderby any of the above. I would also like to be able to "Sort" Ascending or descending based on user's choice. I would also like to use Paging on the result set.

How to use a dynamic linq query to achieve the above. I'm googling and i see some PredicateBuilder class available for the filter (where clause) part. Can anyone help me on how i can achieve the above using PredicateBuilder class or any other way.

解决方案

//data to be queried
List<Dictionary<string, object>> listOfStuff = new List<Dictionary<string, object>>()
{   new Dictionary<string,object> { {"Source", "srchostname1"}, {"Destination", "destination"}, {"State","Transferring"}, {"Created", DateTime.Parse("01/02/2010 12:32:20pm") } },
    new Dictionary<string,object> { {"Source", "srchostname2"}, {"Destination", "destination2"}, {"State","Error"}, {"Created", DateTime.Parse("02/02/2010 12:32:20pm")}},
    new Dictionary<string,object> { {"Source", "srchostname3"}, {"Destination", "destination3"}, {"State","Error"}, {"Created", DateTime.Parse("04/02/2010 12:32:20pm")}}
};

// filters to be applied: name and value...
List<Tuple<string, object>> filters = new List<Tuple<string, object>>()
{
    new Tuple<string, object>("Source", "srchostname1"),
    new Tuple<string, object>("State", "Transferring")
};

//sort order arguments: field name, ordinal (in sort args), ascending (false) or descending (true)
List<Tuple<string, int, bool>> sortArguments = new List<Tuple<string, int, bool>>
{
    new Tuple<string, int, bool>("Source", 1, false),
    new Tuple<string, int, bool>("Destination", 2, true)
};

//turn the list into a query
var query = listOfStuff.AsQueryable();

//apply filters
foreach (Tuple<string, object> filter in filters)
{
    string fieldName = filter.Item1;
    object fieldValue = filter.Item2;
    query = query.Where(d => d.Any(v => v.Key == fieldName && v.Value == fieldValue));
}

// apply sort arguments (in descending order)
foreach (Tuple<string, int, bool> sortArg in sortArguments.OrderByDescending(o => o.Item2))
{
    string orderByCol = sortArg.Item1;
    bool descendingOrder = sortArg.Item3;

    if (descendingOrder == false)
    {
        query = query.OrderBy(o => o[orderByCol]);
    }
    else
    {
        query = query.OrderByDescending(o => o[orderByCol]);
    }
}

//execute the query and turn results into a list
var result = query.ToList();

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