LinQ to Object 有关于Dictionary、SQL（LEFT OUTER JOIN \ Group OrderBy Sum） 操作

Dictionary操作

 

c#

var vhe = new Dictionary<String,String>();

var queryString = context.Request.QueryString;

foreach ( string item in queryString ) {

vhe.Add ( item , CommonFunc.ConvertObjectToString ( queryString[item] ) );

}

return vhe;

对以上C#代码用LinQ To Object 进行Coding

 

LinqToObject

1:

  var query = from item in queryString.OfType<String> ()

              select new KeyValuePair<string , string> ( item , queryString[item] );

  var vhe = new Dictionary<String , String> ();

  foreach ( var item in query ) {
        vhe.Add ( item.Key.ToString () , item.Value.ToString () );
  }

  return vhe;

2:

   return queryString.OfType<String> ()

                     .ToDictionary ( item => item , item => queryString[item] );

LEFT OUTER JOIN 操作

 

SQL:

SELECT  [t0].[MemberID], [t0].[MemberName] 
FROM    [dbo].[MemberInfo] AS [t0] 
LEFT OUTER JOIN [dbo].[MemberSort] AS [t1] ON ( [t1].[MemberType] = 0 ) AND 
                                              ( [t0].[MemberID] = [t1].[MemberID] ) 
ORDER BY ( CASE WHEN [t1].[SortNumber] IS NOT NULL THEN [t1].[SortNumber] 
                ELSE 9999 
           END )

LINQ：

var data = from m in db.MemberInfo
           join s in db.MemberSort on m.MemberID equals s.MemberID
           into x
           from cx in x.Where(d => d.MemberType == 0).DefaultIfEmpty()
           orderby cx.SortNumber.HasValue ? cx.SortNumber.Value : 9999
           select m;

Group OrderBy Sum操作

SQL：

SELECT  [SID], CID, SUM(VisitCount), SUM(ResultCount), SUM(ValidCount) 
FROM    dbo.CountVisit 
WHERE   ReportDate BETWEEN '2010-03-04' AND '2010-03-08' AND 
        [SID] LIKE '%m%' 
GROUP BY [sid], CID 
ORDER BY [SID], CID

LINQ：

var list = new List<CountVisitEntity> ();

using ( var tb = GetCountVisitByParam ( svcp , ref flipPageOption ) ) {

       if ( tb.Rows.Count > 0 ) {

            var query = from item in tb.AsEnumerable ()
                        group item by new { SID = item.Field<String> ( "SID" ) ,
                                            CID = item.Field<String> ( "CID" )
                                          } into result
                        orderby result.Key.SID , result.Key.CID
                        select new CountVisitEntity () {
                             SID = result.Key.SID ,
                             CID = result.Key.CID ,
                             XX = result.Sum ( o => o.Field<Int32> ( "XX" ) ) ,
                             XXX = result.Sum ( o => o.Field<Int32> ( "XXX" ) ) ,
                             XXXX = result.Sum ( o => o.Field<Int32> ( "XXXX" ) )
                        };
           list = query.ToList ();
      }
}

return list;