[RESOLVED] Coloring Text after percentage calculation

Hello,

I'm calculate the persentage between two numbers.
After the calculation I want that the positive numbers are green and the others red.

It's working good, but the numbers -0.25 are still green instead of red.
How can I change that?

Here's my code for calculation and coloring the text:

Code:

---

  Dim C1 As String = TextBox11.Text
        Dim D1 As String = TextBox1.Text
        Dim percentage As Decimal = Val(D1 - C1) / C1 * 100

        TextBox16.Text = String.Format("{0:0.00}", percentage) & " " & "%"

        If Val(TextBox16.Text) >= 0.00 Then

            TextBox16.Font = New Font("Adobe Devanagari", 11.0, FontStyle.Bold)
            TextBox16.ForeColor = Color.DarkGreen
        Else

            TextBox16.Font = New Font("Adobe Devanagari", 11.0, FontStyle.Bold)
            TextBox16.ForeColor = Color.Red
         
        End If

---

Thanks in advance,

There's a lot to unpack there... so I'll try to break it down:

Code:

---

Dim C1 As String = TextBox11.Text
Dim D1 As String = TextBox1.Text

---

First, C1 and D1 are strings... but you then use them for mathematical calculations. They should be Decimal at the least, and you should use Decimal.TryParse() to convert the text into numbers.

Code:

---

Dim percentage As Decimal = Val(D1 - C1) / C1 * 10

---

By the time you use Val here, it's too late... at the least it should be (Val(D1) - Val(C1)) ....

Code:

---

If Val(TextBox16.Text) >= 0.00 Then

---

Here you are using Val again... when you calculated percentage in the line above.... Why not use it again here?

Which brings me to the final thing: don't use Val... it has issues, and one of those is what you're running into.
Val returns all numerics up to the first non-numeric character... so Val("123.456") returns 123.... Val("C123") returns 0.... and Val("-0.25") returns....... 0. The "-" doesn't register as a numeric. That's why you should avoid it unless you know what you're dealing with. Use .TryPArse instead.

Code:

---

Dim C1, D1 as Decimal
Decimal.TryParse(Textbox11.text, C1)
Decimal.TryParse(Textbox1.text, D1)
Dim percentage as DEcimal = (D1-C1)/C1 * 100

TextBox16.text = String.Format("{0:0.00} %", percentage)

If percentage >= 0.00 then
  TextBox16.Font = New Font("Adobe Devanagari", 11.0, FontStyle.Bold)
  TextBox16.ForeColor = Color.DarkGreen
Else
  TextBox16.Font = New Font("Adobe Devanagari", 11.0, FontStyle.Bold)
  TextBox16.ForeColor = Color.Red
End If

---

I think I have that right... been a while since I've used TryPArse though...

-tg

Quote:

---

Originally Posted by techgnome

There's a lot to unpack there... so I'll try to break it down:

Code:

---

Dim C1 As String = TextBox11.Text
Dim D1 As String = TextBox1.Text

---

First, C1 and D1 are strings... but you then use them for mathematical calculations. They should be Decimal at the least, and you should use Decimal.TryParse() to convert the text into numbers.

Code:

---

Dim percentage As Decimal = Val(D1 - C1) / C1 * 10

---

By the time you use Val here, it's too late... at the least it should be (Val(D1) - Val(C1)) ....

Code:

---

If Val(TextBox16.Text) >= 0.00 Then

---

Here you are using Val again... when you calculated percentage in the line above.... Why not use it again here?

Which brings me to the final thing: don't use Val... it has issues, and one of those is what you're running into.
Val returns all numerics up to the first non-numeric character... so Val("123.456") returns 123.... Val("C123") returns 0.... and Val("-0.25") returns....... 0. The "-" doesn't register as a numeric. That's why you should avoid it unless you know what you're dealing with. Use .TryPArse instead.

Code:

---

Dim C1, D1 as Decimal
Decimal.TryParse(Textbox11.text, C1)
Decimal.TryParse(Textbox1.text, D1)
Dim percentage as DEcimal = (D1-C1)/C1 * 100

TextBox16.text = String.Format("{0:0.00} %", percentage)

If percentage >= 0.00 then
  TextBox16.Font = New Font("Adobe Devanagari", 11.0, FontStyle.Bold)
  TextBox16.ForeColor = Color.DarkGreen
Else
  TextBox16.Font = New Font("Adobe Devanagari", 11.0, FontStyle.Bold)
  TextBox16.ForeColor = Color.Red
End If

---

I think I have that right... been a while since I've used TryPArse though...

-tg

---

Code:

---

Dim C1, D1 as Decimal
if Decimal.TryParse(Textbox11.text, C1) AndAlso Decimal.TryParse(Textbox1.text, D1) Then
    Dim percentage as Decimal = (D1-C1)/C1 * 100

    TextBox16.text = String.Format("{0:0.00} %", percentage)

    If percentage >= 0.00 then
        TextBox16.Font = New Font("Adobe Devanagari", 11.0, FontStyle.Bold)
        TextBox16.ForeColor = Color.DarkGreen
    Else
        TextBox16.Font = New Font("Adobe Devanagari", 11.0, FontStyle.Bold)
        TextBox16.ForeColor = Color.Red
    End If
Else
    TextBox16.Font = New Font("Adobe Devanagari", 11.0, FontStyle.Bold)
    TextBox16.ForeColor = Color.Black
    TextBox16.text = "Invalid input"
End If

---

Quote:

---

Originally Posted by techgnome

... so Val("123.456") returns 123.... Val("C123") returns 0.... and Val("-0.25") returns....... 0. The "-" doesn't register as a numeric. ...

---

Only one of those examples is true.
Val returns a Double, so Val("123.456") returns a double set to 123.456, and Val("-0.25") returns a double set to -0.25.
It isn't locale sensitive, so if you use commas instead of periods for the decimal point, it won't convert correctly.

I'm not saying to use Val, as it is a holdover from legacy VB, but to think that a decimal point (which must be a period) and a negative sign are not considered part of a numeric string is rather a surprising belief to hold.

I'ts working fine.
The Textbox is coloring like I wanted.
The're is however a problem after closing and reopening the form.
Then the Textbox is coloring Black.

What can I do to save those colors?

You need to save the information at an upper level. if you create an instance of the form (initialization of all variables), deal with it (modify your variables and properties) and close it (reset all value) , you remove all information that are not in the initial properties of the form. So you need to save the information you want in variables external to that form, so you can keep them and call them when you load the form.

or you can also hide the form instead of closing it so the instance is still the same and the value are not reset.

regards

Hello,

After some search I added this code to the Form Load.

Code:

---

Dim percentage as Decimal = Val(Textbox16.Text)

    If percentage >= 0.00 then
        TextBox16.Font = New Font("Adobe Devanagari", 11.0, FontStyle.Bold)
        TextBox16.ForeColor = Color.DarkGreen
    Else
        TextBox16.Font = New Font("Adobe Devanagari", 11.0, FontStyle.Bold)
        TextBox16.ForeColor = Color.Red
    End If

---

Thanks for helping.