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:

 

代码

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;