WFA - C# and TreeView from SQL Server

Question

I have populating a treeView control in a windows application using SQL Server and C#:

CREATE TABLE [dbo].[myTable]
(
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [title] [varchar](255) NOT NULL,
    [parentID] [int] NULL, 

    CONSTRAINT [PK_myTable] 
        PRIMARY KEY CLUSTERED ([ID] ASC)
)

Insert some hierarchal data

SET IDENTITY_INSERT myTable ON 
GO 

INSERT INTO myTable(ID, title, parentID) 
VALUES(1, 'Microsoft', NULL) 

INSERT INTO myTable(ID, title, parentID) 
VALUES(2, 'C#', 1) 

INSERT INTO myTable(ID, title, parentID) 
VALUES(3, 'VB.net', 1) 

INSERT INTO myTable(ID, title, parentID) 
VALUES(4, 'Open Source', NULL) 

INSERT INTO myTable(ID, title, parentID) 
VALUES(5, 'Python', 4) 

INSERT INTO myTable(ID, title, parentID) 
VALUES(6, 'Ruby', 4) 

INSERT INTO myTable(ID, title, parentID) 
VALUES(7, 'PHP', 4) 

INSERT INTO myTable(ID, title, parentID) 
VALUES(8, 'Perl', 4) 

INSERT INTO myTable(ID, title, parentID) 
VALUES(9, 'Java', 4) 

INSERT INTO myTable(ID, title, parentID) 
VALUES(10, 'LinQ', 2) 

INSERT INTO myTable(ID, title, parentID) 
VALUES(11, '5.2', 7) 

INSERT INTO myTable(ID, title, parentID) 
VALUES(12, '4.4', 7) 
GO 

SET IDENTITY_INSERT myTable OFF 
GO

Define a root value

CREATE PROCEDURE viewMyTable 
AS 
BEGIN
    SELECT ID, title, ISNULL(parentID, 0) AS parentID
    FROM myTable 
END

Add a same table key contraint.

ALTER TABLE [dbo].[myTable] WITH CHECK 
    ADD CONSTRAINT [FK_myTable_myTable] 
    FOREIGN KEY([parentID]) REFERENCES [dbo].[myTable] ([ID]) 
GO 

ALTER TABLE [dbo].[myTable] CHECK CONSTRAINT [FK_myTable_myTable]

And there is nothing in treeview. Can anyone help me?

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Answer 1

Hope this help you.

WITH f(ID, Title, Level, Sort)
AS(
    SELECT ID, Title, 0 AS Level, ROW_NUMBER() OVER(ORDER BY ID) AS Sort
    FROM myTable
    WHERE parentID IS NULL

    UNION ALL

    SELECT B.ID, B.Title, A.Level + 1, A.Sort
    FROM f A, myTable B
    WHERE A.Id = B.parentID
)
SELECT * 
FROM f 
ORDER BY Sort, Level