While applying opacity to a form should we use a decimal or double value?

Question: I want to use a track-bar to change a form's opacity.
This is my code:

decimal trans = trackBar1.Value / 5000;
this.Opacity = trans;

When I build the application, it gives the following error:

Cannot implicitly convert type 'decimal' to 'double'.

I tried using trans and double but then the control doesn't work. This code worked fine in a past VB.NET project.

Solution:

An explicit cast to double isn't necessary.

double trans = (double)trackBar1.Value / 5000.0;

Identifying the constant as 5000.0 (or as 5000d) is sufficient:

double trans = trackBar1.Value / 5000.0;
double trans = trackBar1.Value / 5000d;