Load hour and minute to datagridview C#

Here's some sample code to give you an idea of how to accomplish this:
 
 
// Get the start time and end time inputs and the selected meeting room
DateTime startTime = dateTimePickerStart.Value;
DateTime endTime = dateTimePickerEnd.Value;
string selectedRoom = comboBoxRooms.SelectedItem.ToString();

// Loop through the rows in the DataGridView and find the matching row
foreach (DataGridViewRow row in dataGridView1.Rows)
{
    if (row.Cells[0].Value.ToString() == selectedRoom)
    {
        // Loop through the columns and compare the start and end times with the time slots
        for (int i = 1; i < dataGridView1.Columns.Count; i++)
        {
            DateTime columnTime = DateTime.ParseExact(dataGridView1.Columns[i].HeaderText, "HH:mm", null);
            if (startTime <= columnTime && endTime >= columnTime)
            {
                MessageBox.Show("The selected time slot is already booked.");
                return;
            }
        }
    }
}

// If the code reaches this point, the selected time slot is available and can be added to the DataGridView

Keep in mind this code assumes that the DataGridView has been populated with data and that the start and end time inputs are represented as DateTime objects. You may need to modify the code to fit your specific scenario.