How to set invterval for the trackbar in C# winforms.

The 'Value Property of the TrackBar is continuous from 'MinimumValue to 'MaximumValue.

To simulate detents (snap-to-values) you need to implement a TrackBar 'ValueChanged EventHandler like this:

private int smallChangeValue = 5;
private int trackValue;
private bool blockRecursion = false;

private void trackBar1_ValueChanged(object sender, EventArgs e)
{
    if (blockRecursion) return;

    trackValue = trackBar1.Value;

    if (trackValue % smallChangeValue  != 0)
    {
        trackValue = (trackValue / smallChangeValue) * smallChangeValue;

        // see note #1 below
        blockRecursion = true;

            trackBar1.Value = trackValue;

        blockRecursion = false;
    }

    // for debugging only
    // textBox1.Text = trackValue.ToString();
}

If you examine what's happening here, you can see this is just doing a simple form of rounding-off (rounding-down actually) of the TrackBar value.

note #1: in this example the setting a flag to block recursion is not really necessary; the reason this is shown is in case you want to do a bit more sophisticated handling such as: examining the modulo remainder of value and small-change value, and, in case it's closer to the next value, rounding-up.