如何使用 vb.net 删除一段 INI 文件中的一行？

Question

I am trying to delete a row inside the section of an INI file, but after triggering the delete code, The INI file contents stays the same. The deleted data of the INI File does not appear to be deleted.

CODE:

  <DllImport("kernel32.dll", SetLastError:=True)> _
    Public Shared Function WritePrivateProfileSection( _
        ByVal lpAppName As String, _
        ByVal lpString As String, _
        ByVal lpValue As String, _
        ByVal lpFileName As String) As Boolean
    End Function   

    Public Sub DeleteSection(ByRef sApp As String, ByRef sKey As String)
        Try
            Dim ret As Boolean
            Dim sBuff As New System.Text.StringBuilder
            sBuff.Capacity = 256

            ret = WritePrivateProfileSection(sApp, sKey, "", m_sIniFile)
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub

USAGE:

m_ini.DeleteSection("AppName", "AppKey")

The main purpose of this is to Delete the key and its value.

But the problem is after deleting it, nothing has changed on the INI File.

Regards,

Answer 1

EDIT:

As pointed out by Jimi in the comments, WritePrivateProfileString can delete a key. It appears that you should indeed be calling WritePrivateProfileString rather than WritePrivateProfileSection and the third argument should be Nothing rather than an empty String .

Also, while the actual names don't matter when executing, it's a good idea to be consistent in your code to avoid confusion. As such, the parameters, in order, should be lpAppName , lpKeyName , lpString and lpFileName . If you want to use .NET-style naming instead, use appName , keyName , [string] and fileName . You might use value instead of [string] to avoid the need to escape a keyword.

ORIGINAL:

I've never used either so I'm not completely confident in this answer but, from what I can see, you are mangling WritePrivateProfileSection and WritePrivateProfileString into a combination that doesn't do either. Your function is named WritePrivateProfileSection but that function has three parameters, not four. It is WritePrivateProfileString that has four but that doesn't do what you want.

WritePrivateProfileString will write a value to a key, which is fine if you want to clear that key but if you want to delete it, it's not right. WritePrivateProfileSection takes a single String containing all the keys and values to write to a section so that's what you need to use and you need to omit the key you want deleted from that String .

It appears that what you actually need to do is read all the keys and values in that section and then construct a String from them, leaving out the key you want to delete. You then call WritePrivateProfileSection with that String to overwrite the section with the modified data. The GetPrivateProfileSection function will get a String containing all the current keys and values, so you should call that, process the result and then pass the manipulated data to WritePrivateProfileSection .

Answer 2

I also recommend using WritePrivateProfileString, but you should declare it correct.

' Writes String values
<DllImport("Kernel32.dll", CharSet:=CharSet.Unicode,
           SetLastError:=True, EntryPoint:="WritePrivateProfileStringW")>
Public Shared Function WritePrivateProfileString(
    Section As String,
    Key As String,
    WriteStr As String,
    IniFile As String) As Integer
End Function

In .NET the standard is Unicode, so use the EntryPoint with the W ending (= wide)

Then deleting of a Key/Entry is easy:

Public Sub DeleteEntry(IniFile As String, Section As String, Key As String)
    WritePrivateProfileString(Section, Key, vbNullString, IniFile)
End Sub

You could also delete a complete section with WritePrivateProfileString:

Public Sub DeleteSection(IniFile As String, Section As String)
    WritePrivateProfileString(Section, vbNullString, vbNullString, IniFile)
End Sub