從MSDN文章我讀我應該使用StringBuilder而不是串聯一個正常的字符串。但是我不知道爲什麼我會得到下面的錯誤:「在變量'ShowString'被使用之前,它已經被分配了一個值。在運行時會導致一個空引用異常。在賦值之前使用變量?
下面的代碼:
Dim ShowString As StringBuilder
Dim ShowSort As StringBuilder
'ShowString.
ShowString.Append("POS,tdate,Product")
'========Show Options==================
If CheckBox1.Checked = True Then
ShowString.Append(",tkey")
End If
If CheckBox2.Checked = True Then
ShowString.Append(",Price")
End If
If CheckBox3.Checked = True Then
ShowString.Append(",FID")
End If
'==========End Show Options============
'=========Sort Options================
If RadioButton1.Checked = True Then
ShowSort.Append("tdate")
If RadioButton8.Checked Then
ShowSort.Append(" desc")
End If
End If
If RadioButton2.Checked = True Then
ShowSort.Append("tkey")
If RadioButton8.Checked Then
ShowSort.Append(" desc")
End If
End If
'=======End Sort Options=============
Dim sort As String = ShowSort.ToString
Dim show As String = ShowString.ToString
Try
con.Open()
Catch ex As Exception
MessageBox.Show("Please contact support, there was a database error with the following message: " & ex.Message, "Cannot Connect", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try
無關,與SB。 – Will 2012-04-03 15:50:43