VB.NET参数没有默认值

Question

创建此代码以将项目作为emp_state插入到表名中，问题出在@ d3中，当我从组合框中选择项目时，它给出了参数@ d3没有默认值的错误？

这是代码，请给我一个解决方案

Dim sSQL As String = "insert into emp_state(Badge,Name,State,Date_of_Join,Date_of_Termination,Reasons,Information) values (@d1,@d2,@d3,@d4,@d5,@d6,@d7)"
            Dim cmd As OleDbCommand = New OleDbCommand(sSQL, cn)


        ' Badge
        Dim Badge As OleDbParameter = New OleDbParameter("@d1", OleDbType.VarWChar, 8)
        Badge.Value = TextBox1.Text.ToString()
        cmd.Parameters.Add(Badge)

        ' Name
        Dim Name As OleDbParameter = New OleDbParameter("@d2", OleDbType.VarWChar, 50)
        Name.Value = TextBox2.Text.ToString()
        cmd.Parameters.Add(Name)

        ' State
        ComboBox1.SelectedIndex = 0
        Dim State As OleDbParameter = New OleDbParameter("@d3", OleDbType.VarWChar, 20)
        ComboBox1.SelectedIndex = ComboBox1.Items.IndexOf("State")
        cmd.Parameters.Add(State)


        'Date_of_Join
        Dim Date_of_Join As OleDbParameter = New OleDbParameter("@d4", OleDbType.Date, 15)
        Date_of_Join.Value = dtpDOB.Text.ToString()
        cmd.Parameters.Add(Date_of_Join)

        'Date_of_Termination
        Dim Date_of_Termination As OleDbParameter = New OleDbParameter("@d5", OleDbType.Date, 15)
        Date_of_Termination.Value = DateTimePicker1.Text.ToString()
        cmd.Parameters.Add(Date_of_Termination)

        'Reasons
        Dim Reasons As OleDbParameter = New OleDbParameter("@d6", OleDbType.VarWChar, 9999)
        Reasons.Value = TextBox3.ToString()
        cmd.Parameters.Add(Reasons)

        'Information
        Dim Information As OleDbParameter = New OleDbParameter("@d7", OleDbType.VarWChar, 9999)
        Information.Value = TextBox4.ToString()
        cmd.Parameters.Add(Information)

Answer 1

   ' State
    ComboBox1.SelectedIndex = 0
    Dim State As OleDbParameter = New OleDbParameter("@d3", OleDbType.VarWChar, 20)
    ComboBox1.SelectedIndex = ComboBox1.Items.IndexOf("State")
    cmd.Parameters.Add(State)

再次阅读本部分。

1. 您将组合框设置为选择第一个项目
2. 然后您创建参数
3. 然后通过尝试查找某个项目将组合框的索引设置为索引？
4. 然后将空参数添加到parameterList

我想你想做的是：

   ' State
    ' ComboBox1.SelectedIndex = 0
    Dim State As OleDbParameter = New OleDbParameter("@d3", OleDbType.VarWChar, 20)
    State.Value = ComboBox1.SelectedItem.Value
    cmd.Parameters.Add(State)