how to solve Conversion from string "" to type 'Double' is not valid.

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VB

Private Sub Timer30_Tick(sender As Object, e As EventArgs) Handles Timer30.Tick
Second = Second + 1
        If Second >= 30 Then
            Timer30.[Stop]()
            MessageBox.Show("Time Up ")
        End If
            Dim ScreenSize As Size = New Size(My.Computer.Screen.Bounds.Width, My.Computer.Screen.Bounds.Height)
            Dim BMP As New Bitmap(My.Computer.Screen.Bounds.Width, My.Computer.Screen.Bounds.Height)
            Dim g As System.Drawing.Graphics = System.Drawing.Graphics.FromImage(BMP)
            g.CopyFromScreen(New Point(0, 0), New Point(0, 0), ScreenSize)
        Dim DirectoryA As String = FileDirectory.Text
        Dim Frame1 As String = FileNumber.Text
        Dim img1 As String = FileType.Text
        FileNumber.Text = FileNumber.Text + 1 'i am getting errors at this point
                          'Conversion from string "" to type 'Double' is not valid.

BMP.Save(DirectoryA & Frame1 & img1)

Posted 17-Feb-15 19:44pm

Srikanth59

Updated 17-Feb-15 21:05pm

Maciej Los

v4

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Comments

[no name] 18-Feb-15 1:51am

You wanted to convert "" ? or replace the ""?

Srikanth59 18-Feb-15 2:32am

i want to convert into string format into double as error showed

Sergey Alexandrovich Kryukov 18-Feb-15 2:43am

If your input is "!@@$@$^%@!@#!", what is the "converted" double value should be? :-)
—SA

Srikanth59 18-Feb-15 3:59am

am getting errors
A first chance exception of type 'System.InvalidCastException' occurred in Microsoft.VisualBasic.dll

Additional information: Conversion from string "" to type 'Double' is not valid.

make sure the source type is convertible to the destination type.

Sergey Alexandrovich Kryukov 18-Feb-15 10:58am

Sure. Did you understand my comment you replied to?
—SA

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Maciej Los · Answer 1 · 2015-02-17T20:10:00

Solution 1

You're trying to convert text to numeric value:

VB

FileNumber.Text = FileNumber.Text + 1

Instead of it, use this:

VB

'on the beginning of the function
Dim counter As Integer = 0
'later
If Int32.TryParse(FileNumber.Text, counter) Then
    counter+=1
    FileNumber.Text = counter.ToString()
End If

For further information, please see: Int32.TryParse Method (String, Int32)[^]

Posted 17-Feb-15 20:10pm

Maciej Los

Updated 17-Feb-15 20:14pm

v2

Comments

Sergey Alexandrovich Kryukov 18-Feb-15 2:44am

Sure, a 5.
—SA

Maciej Los 18-Feb-15 3:04am

Thank you, Sergey ;)

Srikanth59 18-Feb-15 5:06am

i tried above code but it doesn't display any information in the textbox and it just shows me nothing when i executed

Maciej Los 18-Feb-15 5:39am

Debug the code and find out why it happens.