ExecuteNonQuery正在引发异常默认参数的使用无效

Question

当我在vb.net中传递Nothing作为参数时，ExecuteNonQuery抛出异常。它不允许我插入空值

Dim id=无Dim sqlStr＝"；插入学生的Id=">

cmd.Parameters.AddawithValue("？"，id(cmd。ExecuteNonQuery((

Answer 1

您的示例有点无稽之谈，因为INSERT语句没有WHERE子句。原则仍然有效：

Dim id As Integer?
Dim sql = "UPDATE Student SET Name = @Name WHERE Id = @Id"
Dim command As New OleDbCommand(sql, connection)
With command.Parameters
.Add("@Name", OleDbType.VarChar, 50).Value = name
.Add("@Id", OleDbType.Integer).Value = If(id.HasValue, id.Value, CObj(DBNull.Value))
End With