
数据库如上ID=3的是 空值 在操作数据库的时候不可避免的出现
读取数据库某一字段的 数据 我的代码如下
Dim con As New OleDb.OleDbConnection
Dim cmdn As New OleDb.OleDbCommand
Dim wellname As Array
Dim num As Integer
con.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\wq\Desktop\实例.accdb;Persist Security Info=False"
cmdn.Connection = con
cmdn.CommandText = "Select W1 from treeview "
con.Open()
Dim dan As New OleDb.OleDbDataAdapter
dan.SelectCommand = cmdn
Dim dsn As New DataSet
dan.Fill(dsn)
Dim dtn As DataTable = dsn.Tables(0)
num = dtn.Rows.Count
wellname = Array.CreateInstance(GetType(String), num)
Dim i As Integer
For i = 0 To num - 1
If dtn.Rows(i).Item(0) <> "" Then
wellname(i) = dtn.Rows(i).Item(0)
End If
Next
con.Close()
If dtn.Rows(i).Item(0) <> "" Then 这句是我加的 但是出现这个

那么这个判断语句要怎么加呢
------解决思路----------------------
写成这样的试试
If dtn.Rows(i)(0).ToString() <> "" Then
wellname(i) = dtn.Rows(i)(0).ToString()
End If
或者这样的
If String.IsNullOrEmpty(dtn.Rows(i)(0).ToString()) = False Then
wellname(i) = dtn.Rows(i)(0).ToString()
End If
------解决思路----------------------
更正:b)VB.Net下专门的判断函数
If Not IsDBNull(dtn.Rows(i).Item(0)) Then