未处理的 VB.Net 异常：System.Runtime.InteropServices.ExternalException：'GDI+ 中发生一般错误

Question

I'm trying to save a plot I write on Vb.Net 6.0 (Visual Studio 2022) to a.png file.

bmp.Save("C:\graph.png", System.Drawing.Imaging.ImageFormat.Png)

However, in the above code segment, I get the following exception unhandled message:

VB.Net Exception Unhandled:

System.Runtime.InteropServices.ExternalException: 'A generic error occurred in GDI+

This is the rest of the script to which the code segment belongs to

Imports System.Security
Imports System.Security.Permissions
Imports System.Drawing.Bitmap
Imports System.Drawing.Imaging



Public Class Form1
    Dim m, i As Integer
    Dim h, Pi, Pi2, u, v, x, y As Single
    Dim left As Integer = Me.left

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    End Sub

    Dim top As Integer = Me.top
    Dim centerX As Integer = Me.left + (Me.Width / 2)
    Dim centerY As Integer = Me.top + (Me.Height / 2)
    Dim bmp As New Bitmap(Me.Width, Me.Height)
    Dim path As String = "C:\graph.png"
    Dim perm As FileIOPermission = New FileIOPermission(FileIOPermissionAccess.Write, path)



    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim g As Graphics = Graphics.FromImage(bmp)
        m = 1000
        h = 1 / 100
        Pi = 3.14
        Pi2 = 3.14 * 2
        x = 150
        y = 150

        For i = 1 To m
            u = x * Cos(h * Pi2) + y * Sin(h * Pi2)
            v = y * Cos(h * Pi2) - x * Sin(h * Pi2)
            x = u
            y = v
            g.FillRectangle(New SolidBrush(Color.FromArgb(255, 0, 0)), x, y, 1, 1)
        Next i
        Try
            perm.Demand()
            ' The application has permission to write to the file
            bmp.Save("C:\graph.png", System.Drawing.Imaging.ImageFormat.Png)
        Catch ex As SecurityException
            ' The application does not have permission to write to the file
        End Try

    End Sub
End Class

Answer 1

Have you tried running your app with administrator privileges?

Starting with Windows 10, Windows doesn't want you to save files to the root of your C drive. So you should choose a different directory to save the file.