Question

我的数据库ms-access包含表＆＃39;客户端＆＃39;这个表包含：（ClientName，ClientPhone，ClientAddress，ClientCredit，ClientDes）__ ok！我想在我的软件vb.net中添加ClientCredit的所有值。我使用这个代码和它的工作，但我给它一个错误的价值!!

Dim credit As Double = 0    
Try
    Dim dt As DataTable = New DBConnect().selectdata( _
          "SELECT ClientName, ClientPhone, ClientAddress, ClientCredit, ClientDes FROM Client;")
    For i As Integer = 0 To dt.Rows.Count - 1
        credit = dt.Rows(0)(3).ToString + credit
    Next
Catch ex As Exception
    MessageBox.Show(ex.Message)
End Try
FlatTextBox1.Text = credit

此代码给出结果：400但实际结果是415.2

Answer 1

您不在循环中使用索引i。将代码修改为Rows（i）而不是Rows（0）

   For i As Integer = 0 To dt.Rows.Count - 1
        //credit = dt.Rows(0)(3).ToString + credit                   
        // credit is double, why ToString 
        credit = Convert.ToDuble(dt.Rows(i)(3)) + credit          
    Next

其他解决方案：

您可以避免循环（删除..next）并使用DataTable的Compute方法：

     credit = dt.Compute("Sum(ClientCredit)", "");

Answer 2

你的求和线：

credit = dt.Rows(0)(3).ToString + credit

应该阅读

credit += TryCast(dt.Rows(i)(3), Double)

从ms-access获取值并添加所有值Vb.Net

2 个答案: