Conversion of String to type double - asp.net

Question

I am having a simple drop down list as shown below which contains some values:
<select id="Opacity">
<option value="50">50%</option>
<option value="100">100%</option>
</select>
Now I am passing the selected value using ajax call to my webmethod:
$("#btnGetFiles").click(function () {
ClearImages();
$.ajax({
type: "POST",
url: "Default.aspx/GetFiles",
data: JSON.stringify({imgOpacity: $('#Opacity').val()}),
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (response) {
}
});
});
Now in my webmethod I'm, getting the value as "50" if I select the drop down value as "50"
Here my problem arises that I have the below code where I need to set that opacity:
Dim imageOpacity As Single = 0.0F
imageOpacity = CInt(imgOpacity)
imageOpacity = imgOpacity / 100
imageOpacity = 1 - imgOpacity
Dim colorMatrixElements As Single()() = {New Single() {1.0F, 0.0F, 0.0F, 0.0F, 0.0F},
New Single() {0.0F, 1.0F, 0.0F, 0.0F, 0.0F},
New Single() {0.0F, 0.0F, 1.0F, 0.0F, 0.0F},
New Single() {0.0F, 0.0F, 0.0F, imageOpacity , 0.0F},
New Single() {0.0F, 0.0F, 0.0F, 0.0F, 1.0F}}
Dim wmColorMatrix As New ColorMatrix(colorMatrixElements)
Now I need to add "%" to the "imgOpacity".If I try to do this way CInt(imgOpacity + "%") it throws me an error stating that string cannot be converted to type "Double".
So how do I rectify this?

Answer 1

Why don't you just divide the value by 100? Is it not what percentage is for?
I think this is a case a typo gone un-noticed as your variable names are very similar.
See this snippet
Dim imageOpacity As Single = 0.0F
imageOpacity = CInt(imgOpacity)
imageOpacity = imgOpacity / 100
imageOpacity = 1 - imgOpacity
Here the R.H.S of the third and fourth statements must take the value from imageOpacity and not from imgOpacity. Change that snippet to this.
Dim imageOpacity As Single = 1 - Convert.ToSingle(imgOpacity) / 100
And after that please assign imageOpacity and not imgOpacity to the matrix again

Answer 2

At last found the answer.
I have changed my code to this:
imageOpacity = Single.Parse(imgOpacity)