get number of hours between two date and two Time - sql

Question

I have a DataGridView contains all the spots with (DateStarttasck, TimeStarttasck) and (DateEndtasck, TimeEndtask) made ​​in a given period (StartDate, EndDate), and I try to calculate the number of hours between (DateStarttasck, TimeStarttasck) and (DateEndtasck, TimeEndtask) during the period (StartDate, EndDate)
NB: DateStarttasck, TimeStarttasck are each separated in DateTimePicker
and same thing for (DateEndtasck, TimeEndtask) (StartDate, EndDate)
so I'm looking at first to do a combinaision between Time and date and then calculate the number of hours
Dim sql As String = "select * from task where id_task = " & Textbox1.Text & " and Datetasck Between '" & DateTimePicker1.Text & "' And '" & DateTimePicker2.Text & "';"
command.CommandText = sql
connection.Open()
Dim ds As New DataSet
Dim SQLAdapter As New MySqlDataAdapter(sql, connStr)
SQLAdapter.Fill(ds, "connectString")
DataGridView1.DataSource = ds
DataGridView1.DataMember = "connectString"
DataGridView1.AutoResizeColumns()
connection.Close()

Answer 1

Use DateTime.TryParse to attempt to convert the date string and time string into a single DateTime object, like this:
Dim dateValue As Date
If Date.TryParse(dateString + " " + timeString, dateValue) Then
' Successfully parsed date and time strings into the dateValue object
Else
' Unable to parse date and time strings
End If
Note: dateString is the date piece from the database and timeString is the time piece from the database.

Answer 2

First of all, add both date and time (start with start) and (end with end)
ex: IN C#
DateTime date_Start = DateTime.Parse(StartDate_txt.Text);
DateTime Time_Start = DateTime.Parse(StartTime_txt.Text);
date_Start.AddHours(double.Parse(Time_Start.Hour));
DateTime date_End = DateTime.Parse(EndDate_txt.Text);
DateTime Time_End = DateTime.Parse(EndTime_txt.Text);
date_End.AddHours(double.Parse(Time_End.Hour));
float Diff = date_End.Subtract(date_Start).Hours
i hope you got the idea sorry,it's in c# but hopefully you get the idea and it's same way in vb