Question

我想为之前有值的字段添加值。我的代码是：

Dim Credits As Integer = Int64.Parse(FinalPay.ToString)
Dim cmd As New SqlCommand("Update Users Set Credit=Credit+" + Credits + 
                          " Where Email ='" + UserEmail + "'", con)

但我收到的错误是：

“从字符串转换为double无效”

Answer 1

如果使用SQL参数，它应该可以正常工作：

Dim cmd As New SqlCommand("UPDATE Users SET Credit = Credit + @Credits Where Email = @Email", con)
cmd.Parameters.Add(New SqlParameter With {.ParameterName = "@Credits", .SqlDbType = SqlDbType.Int, .Value = finalPay})
cmd.Parameters.Add(New SqlParameter With {.ParameterName = "@Email", .SqlDbType = SqlDbType.NVarChar, .Size = 256, .Value = userEmail})

调整每个参数类型（和大小）以匹配数据库中的声明。

Answer 2

Dim Credits As Integer = Int64.Parse(FinalPay.ToString)
Dim cmd As New SqlCommand("Update Users Set Credit=Credit+" & Credits & 
                                                " Where Email ='" & UserEmail & "'", con)

如果你想在vb中连接一个字符串，你想使用“＆amp;”操作

从字符串到Double类型的转换无效

2 个答案: