How to write for loop increase from hour by duration for every iteration ?

Problem

How to write for loop increase from hour by Duration for every iteration ?

I work on windows form application csharp vs2015

i have three textboxes

txt_fromhour 6

txt_tohour 12

txt_Duration 1.5

txt_countduration 4 (calculated as 12-6=6/1.5=4)

I have table name training have 3 fields

serial int

fromhour decimal

tohour decimal

I need to write for loop insert data on three fields as sample below

when i write fromhour 6 and tohour 12 and duration is 1.5 data will inserted as below

serial    fromhour            tohour

1            6                7.5

2            7.5               9

3            9                10.5

4            10.5              12

What I have tried:

for(int i=0;i<=4;i++)

{

insert into training(serial,fromhour,tohour) values(max+1,??,??)

}

Tags: SQL, C# 7.0