CSharp C# Make a non-referenced copy of a string List

CSharp C# Make a non-referenced copy of a string List

Note: this will not work on class objects just primitives like string and int

Key section:

//Make a "copy" - not a reference - of the original list:       List<string> Copy_List = new List<string>(new List<string>(Original_List));

Output from example:

Show Original_List before changes: One Two Three Four Show Copy_List before changes: One Two Three Four Show Original_List after change to original list:  Note: 2nd ordinal value, "Two" will be gone from this list. One Three Four Show Copy_List after change to original list:  Note: 2nd ordinal value, "Two" will NOT be gone from this "copy" of the "original" list. One Two Three Four

Code:

void Main() { //First set up Original list of values: List<string> Original_List = new List<string>(); Original_List.Add("One"); Original_List.Add("Two"); Original_List.Add("Three"); Original_List.Add("Four"); //Make a "copy" - not a reference - of the original list:       List<string> Copy_List = new List<string>(new List<string>(Original_List)); //Show the values before the change: Console.WriteLine("Show Original_List before changes:"); Show_Values(Original_List); Console.WriteLine("Show Copy_List before changes:"); Show_Values(Copy_List); //Remove the 2nd string, ordinal 1, "Two", from the original but not the copy: Original_List.RemoveAt(1); //Show the values after the change: Console.WriteLine("Show Original_List after change to original list:"); Console.WriteLine("  Note: 2nd ordinal value, \"Two\" will be gone from this list."); Show_Values(Original_List); Console.WriteLine("Show Copy_List after change to original list:"); Console.WriteLine("  Note: 2nd ordinal value, \"Two\" will NOT be gone from this \"copy\" of the \"original\" list."); Show_Values(Copy_List); } public void Show_Values(List<string> ListNow) { foreach(string StringNow in ListNow) {       Console.WriteLine(StringNow); } }

SQL Simple example of LEFT JOIN With A WHERE Clause one to many force nulls

SQL Simple example of LEFT JOIN With A WHERE Clause one to many force nulls

Overview:

A LEFT JOIN will normally force nulls on the primary table (with the list of all rows whether there is data or not) results but when you add a WHERE clause on secondary table with the data you no longer get all the values in the primary table so you need to:

1. Send the data table results, using the WHERE clause, into a TABLE variable.
2. Use the Left JOIN on the TABLE variable in step 1 above.

Setup SQL:

use TestRunTracker_T

go  

CREATE TABLE Team_Names (

Team_Name nvarchar(100) NOT NULL

)

use TestRunTracker_T

go

insert into Team_Names select 'one'

insert into Team_Names select 'two'

insert into Team_Names select 'three'

insert into Team_Names select 'four'

use TestRunTracker_T

go  

CREATE TABLE Team_Names_Data (

[RecNumId] [int] IDENTITY(1,1) NOT NULL,

Team_Name nvarchar(100) NOT NULL

)

use TestRunTracker_T

go

insert into Team_Names_Data select 'one'

insert into Team_Names_Data select 'two'

insert into Team_Names_Data select 'four'

Execution SQL:

use TestRunTracker_T

go

declare @Resultsnow TABLE (

[RecNumId] [int] IDENTITY(1,1) NOT NULL,

Team_Name nvarchar(100) NOT NULL

)

INSERT

       @Resultsnow (Team_Name)

     SELECT

Team_Name

     FROM

       Team_Names_Data

     WHERE

       Team_Names_Data.Team_Name = 'two'

select *

from Team_Names A  

left join @Resultsnow B on A.Team_Name = B.Team_Name

Results:

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