如何在 vb.net 中使用 try 和 catch 块？ [关闭]答案

【问题标题】：How do I use a try and catch block in vb.net? [closed]如何在 vb.net 中使用 try 和 catch 块？ [关闭]
【发布时间】：2011-07-18 14:27:00
【问题描述】：

对于下面显示的代码，如果发生错误，我将如何使用 try/catch 块来处理错误？

        TOTKILO.Text = KILO.Text * TOUCH.Text * 0.01
        TextBox10.Text = TextBox9.Text * TextBox8.Text * 0.01
        K = Math.Round(Val(TOTKILO.Text) - Val(TextBox10.Text), 5)
        TextBox11.Text = TextBox7.Text + K

        cmd.CommandType = Data.CommandType.Text
        con.ConnectionString = "Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Documents and Settings\Administrator\My Documents\Visual Studio 2005\Projects\SHOPPROJECT\SHOPPROJECT\shop.mdf;Integrated Security=True;User Instance=True"
        con.Open()
        If RadioButton1.Checked Then
            GOLD = 1
        ElseIf RadioButton2.Checked Then
            SILVER = 1
        End If
        If RadioButton3.Checked Then
            KGOLD = 1
        ElseIf RadioButton4.Checked Then
            KSILVER = 1
        End If
        cmd.CommandText = " INSERT INTO SALES VALUES('" & ComboBox1.Text & " ' , " & SILVER & " ," & GOLD & ",'" & ComboBox2.Text & "'," & KILO.Text & ", " & TOUCH.Text & " ," & TOTKILO.Text & "," & TextBox3.Text & "," & TextBox8.Text & "," & KGOLD & "," & KSILVER & "," & TextBox9.Text & " ," & TextBox10.Text & "," & TextBox11.Text & "," & TextBox12.Text & " , " & TextBox13.Text & " ) "
        cmd.CommandType = " UPDATE BALANCE SET OBBALANCE = " & TextBox11.Text & " WHERE CUSTOMERNAME = '" & ComboBox1.Text & "' "
        cmd.Connection = con
        cmd.ExecuteNonQuery()
        con.Close()
END SUB

我使用 VB.Net 控件和 LINQ to SQL 来执行所有更新和插入，所以当发生错误时我想显示“正确输入数据”，一旦我发现异常，我该怎么做？

【问题讨论】：

请你不要对每个人大喊大叫
how to use a try and catch in vb.net 的可能重复项
并且不要两次发布相同的问题！
我试图在编辑中清理它...我能说什么我是受虐狂
如果你们都打算投票结束他的一个问题，那就改成另一个。这至少做了一些可读性的尝试。

标签： sql vb.net error-handling try-catch

【解决方案1】：

我在下面添加了一个简单的 Try...Catch，但我想你会发现你有很多问题：

您似乎正在对字符串对象进行乘法运算，您应该先解析出数字，然后根据需要将其转换回字符串对象。
您还设置了两次 CommandType，第二次设置为更新命令而不是适当的值。
您的代码对 SQL 注入开放，您不应该通过字符串连接来构建 SQL 语句，而应该使用 sqlparameters
如果您要进行字符串连接，至少使用字符串生成器，但不要进行字符串连接（见上文）
一次性对象（如 SQLCommand）需要放在 Using 块中
不要全部大写
只发布一次您的问题，如果您想添加详细信息，可以在发布后编辑问题

修改后的代码如下：

Try
    TOTKILO.Text = KILO.Text * TOUCH.Text * 0.01
    TextBox10.Text = TextBox9.Text * TextBox8.Text * 0.01
    K = Math.Round(Val(TOTKILO.Text) - Val(TextBox10.Text), 5)
    TextBox11.Text = TextBox7.Text + K
    cmd.CommandType = Data.CommandType.Text
    con.ConnectionString = "Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Documents and Settings\Administrator\My Documents\Visual Studio 2005\Projects\SHOPPROJECT\SHOPPROJECT\shop.mdf;Integrated Security=True;User Instance=True"
    con.Open()
    If RadioButton1.Checked Then
        GOLD = 1
    ElseIf RadioButton2.Checked Then
        SILVER = 1
    End If
    If RadioButton3.Checked Then
        KGOLD = 1
    ElseIf RadioButton4.Checked Then
        KSILVER = 1
    End If
    cmd.CommandText = " INSERT INTO SALES VALUES('" & ComboBox1.Text & " ' , " & SILVER & " ," & GOLD & ",'" & ComboBox2.Text & "'," & KILO.Text & ", " & TOUCH.Text & " ," & TOTKILO.Text & "," & TextBox3.Text & "," & TextBox8.Text & "," & KGOLD & "," & KSILVER & "," & TextBox9.Text & " ," & TextBox10.Text & "," & TextBox11.Text & "," & TextBox12.Text & " , " & TextBox13.Text & " ) "
    cmd.CommandType = " UPDATE BALANCE SET OBBALANCE = " & TextBox11.Text & " WHERE CUSTOMERNAME = '" & ComboBox1.Text & "' "
    cmd.Connection = con
    cmd.ExecuteNonQuery()
Catch (ex as Exception)
    MsgBox.Show("Enter Data Correctly: " & ex.toString)
Finally
    con.Close()
End Try

【讨论】：