c# - 没有为一个或多个必需参数提供值 ERROR

Question

我知道之前有人问过这个问题。我仔细查看了它们，希望找到我遇到问题的原因。

每当我尝试从表单中的表中删除用户时，我都会收到此错误。我可以编辑它们，我只是不能删除它们。我已经进行了研究，试图找出答案，但运气不佳。

html代码:

        <div align="center">
    <asp:Label ID="Label1" runat="server" Text="Manage Users"></asp:Label>
<p>
    <asp:Label ID="Label2" runat="server" Text="User Name:"></asp:Label>
    <asp:TextBox ID="txtUserName" runat="server"></asp:TextBox>
</p>
<p>
    <asp:Label ID="Label3" runat="server" Text="Password:"></asp:Label>
    <asp:TextBox ID="txtPassword" runat="server"></asp:TextBox>
</p>
        <p>
            <asp:Label ID="Label4" runat="server" Text="Security Level:"></asp:Label>
            <asp:DropDownList ID="drpdwnlstSecurityLevel" runat="server" 
                onselectedindexchanged="drpdwnlstSecurityLevel_SelectedIndexChanged">
                <asp:ListItem>A</asp:ListItem>
                <asp:ListItem>U</asp:ListItem>
            </asp:DropDownList>
</p>
        <p>
            <asp:Button ID="btnAddUser" runat="server" onclick="btnAddUser_Click1" 
    Text="Add User" /> 


</p>
        <p>
            <asp:Label ID="lblError" runat="server"></asp:Label>
</p>

    </div>
<p>
    &nbsp;</p>
            <div align="center">
<asp:GridView ID="tblUserLogin" runat="server" AutoGenerateColumns="False" 
    DataSourceID="AccessDataSource1">
    <Columns>
        <asp:BoundField DataField="UserID" HeaderText="UserID" InsertVisible="False" 
            SortExpression="UserID"></asp:BoundField>
        <asp:BoundField DataField="UserName" HeaderText="UserName" 
            SortExpression="UserName"></asp:BoundField>
        <asp:BoundField DataField="UserPassword" HeaderText="UserPassword" 
            SortExpression="UserPassword"></asp:BoundField>
        <asp:BoundField DataField="SecurityLevel" HeaderText="SecurityLevel" 
            SortExpression="SecurityLevel"></asp:BoundField>




        <asp:CommandField ShowEditButton="True"></asp:CommandField>
        <asp:CommandField ShowDeleteButton="True"></asp:CommandField>




    </Columns>
</asp:GridView>
                <asp:AccessDataSource ID="AccessDataSource1" runat="server" 
                    DataFile="~/PayrollSystem_DB.mdb" 

                    SelectCommand="SELECT [UserID], [UserName], [UserPassword], [SecurityLevel] FROM [tblUserLogin]" 
                    DeleteCommand="DELETE FROM [tblUserLogin] WHERE [UserID] = ?" 
                    InsertCommand="INSERT INTO [tblUserLogin] ([UserID], [UserName], [UserPassword], [SecurityLevel]) VALUES (?, ?, ?, ?)" 
                    UpdateCommand="UPDATE [tblUserLogin] SET [UserName] = ?, [UserPassword] = ?, [SecurityLevel] = ? WHERE [UserID] = ?">
                    <DeleteParameters>
                        <asp:Parameter Name="UserID" Type="Int32" />
                    </DeleteParameters>
                    <UpdateParameters>
                        <asp:Parameter Name="UserName" Type="String" />
                        <asp:Parameter Name="UserPassword" Type="String" />
                        <asp:Parameter Name="SecurityLevel" Type="String" />
                        <asp:Parameter Name="UserID" Type="Int32" />
                    </UpdateParameters>
                    <InsertParameters>
                        <asp:Parameter Name="UserID" Type="Int32" />
                        <asp:Parameter Name="UserName" Type="String" />
                        <asp:Parameter Name="UserPassword" Type="String" />
                        <asp:Parameter Name="SecurityLevel" Type="String" />
                    </InsertParameters>
                </asp:AccessDataSource>

                </form>

</body>

Answer 1

您需要设置 gridview 的 DataKeyNames 属性:

datakeynames="UserID"

根据MSDN documentation :

“您必须设置 DataKeyNames 属性，以便 GridView 控件的自动更新和删除功能起作用。这些键字段的值被传递到数据源控件，以指定要更新或删除的行。 "