按字节截取字符串

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim str As String = Me.TextBox2.Text.Trim
        Dim sReturn As String = GetLenString(str, 0, Me.TextBox1.Text)

        MsgBox(sReturn)
    End Sub

"str =需要截取的字符串

"nbegin =截取开始位置

"nlen =截取的长度
    Private Function GetLenString(ByVal str As String, ByVal nbegin As Integer, ByVal nlen As Integer) As String
        If nlen > System.Text.Encoding.Default.GetBytes(str.Trim).Length OrElse nbegin < 0 OrElse nbegin >= str.Trim.Length Then Return ""
        str = str.Substring(nbegin)
        Dim sRnStr As String = ""
        Dim nCount As Integer = 0
        For Each schr As Char In str
            nCount += System.Text.Encoding.Default.GetBytes(schr).Length
            If nCount > nlen Then
                Return sRnStr
            Else
                sRnStr &= schr
            End If
        Next
        Return sRnStr
    End Function