How to change the rows in a datagrid

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Hello to all

i have a datagrid (from sql) with a datatable like this example :

name surname class

rick summer 3
pam Winter 5
erik frost 8

i need to change in this datagrid the column class to other value

if class is like 3 it will show a
if class is like 5 it will show b
if class is like 8 it will show c

i did it with the solution below, but it takes a lot of time when i have a lot rows, around 8000.

can anyone show me a better solution?

thanks in advance

What I have tried:

DataTable dt = Consumptionall(); //from sql connection
 dtAll = dt.Clone();
 dtAll.Columns["class"].DataType = typeof(string);
 foreach (DataRow drdc in dt.Rows)
 {
     dtAll.ImportRow(drdc);
     allconversion();
 }

private void allconversion()
       {
               for (int i = 0; i < dtAll.Rows.Count; i++)
               {
                   if (dtAll.Rows[i]["class"].ToString() == "3")
                   { dtAll.Rows[i]["class"] = "a"; }
                   if (dtAll.Rows[i]["class"].ToString() == "5")
                   { dtAll.Rows[i]["class"] = "b"; }
                   if (dtAll.Rows[i]["class"].ToString() == "8")
                   { dtAll.Rows[i]["class"] = "c"; }

Posted 13-Mar-18 2:42am

drvfn

Updated 13-Mar-18 4:11am

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Richard Deeming · Accepted Answer · 2018-03-13T03:28:00

Solution 1

Use a CASE statement in your SQL query:

SQL

SELECT
    name,
    surname,
    CASE class
        WHEN 3 THEN 'a'
        WHEN 5 THEN 'b'
        WHEN 8 THEN 'c'
        ELSE Convert(varchar(10), class)
    END As class
FROM
    YourTable
;

CASE (Transact-SQL) | Microsoft Docs[^]

Posted 13-Mar-18 3:28am

Richard Deeming

Comments

Maciej Los 13-Mar-18 10:11am

5ed!

Maciej Los · Accepted Answer · 2018-03-13T04:12:00

In addition to solution#1 by Richard Deeming[^], you can add computed/expression column to your DataTable object. Please, read:
Creating Expression Columns | Microsoft Docs[^]
DataColumn.Expression Property (System.Data)[^]

It's quite simple to achieve that:

VB.NET

Dim dc AS DataColumn = New DataColumn("ClassName", Type.GetTYpe("System.String"))
dc.Expression = "IIF(class=3, 'a', IIF(class=5, 'b', IIF(class=8, 'c', 'uknknown')))"
dtAll.Columns.Add(dc)

That's all!