Question

如果在用户点击插入链接按钮后数据库中存在记录，是否可以生成消息框？我希望formview检查记录是否存在，如果没有插入。

非常感谢帮助。在此先感谢：）

以下是我的代码示例：

管理图书

添加/删除书籍

注意：有关图书ID / ISBN，请参阅ISBN中通常所在的条形码在书的后面。需要条形码阅读器。

    <EditItemTemplate>

        Book ID/ISBN:
        <asp:Label ID="bookidLabel1" runat="server" Text='<%# Eval("bookid") %>' />
        <br />

        Title:
        <asp:TextBox ID="booktitleTextBox" runat="server" 
            Text='<%# Bind("booktitle") %>' />
        <br />

        Author's lastname:
        <asp:TextBox ID="lastnameTextBox" runat="server" 
            Text='<%# Bind("lastname") %>' />
        <br />

        Author's firstname:
        <asp:TextBox ID="firstnameTextBox" runat="server" 
            Text='<%# Bind("firstname") %>' />
        <br />

        Description:
        <asp:TextBox ID="descriptionTextBox" runat="server" 
            Text='<%# Bind("description") %>' />
        <br />

        Category:
        <asp:TextBox ID="categoryidTextBox" runat="server" 
            Text='<%# Bind("categoryid") %>' />
        <br />

        Date added:
        <asp:TextBox ID="dateaddedTextBox" runat="server" 
            Text='<%# Bind("dateadded") %>' />
        <br />

        Status:
        <asp:TextBox ID="statusidTextBox" runat="server" 
            Text='<%# Bind("statusid") %>' />
        <br />

        Quantity:
        <asp:TextBox ID="quantityTextBox" runat="server" 
            Text='<%# Bind("quantity") %>' />
        <br />

        name:
        <asp:TextBox ID="nameTextBox" runat="server" Text='<%# Bind("name") %>' />
        <br />
        <asp:LinkButton ID="UpdateButton" runat="server" CausesValidation="True" 
            CommandName="Update" Text="Update" />
        &nbsp;<asp:LinkButton ID="UpdateCancelButton" runat="server" 
            CausesValidation="False" CommandName="Cancel" Text="Cancel" />

    </EditItemTemplate>

    <InsertItemTemplate>

        Book ID:
        <asp:TextBox ID="bookidTextBox" runat="server" Text='<%# Bind("bookid") %>' />
        <asp:RequiredFieldValidator ID="RequesFieldValidator1" runat="server" ErrorMessage="* Required" ControlToValidate="bookidTextBox" ValidationGroup="InsertBook">
        </asp:RequiredFieldValidator>
        <asp:RegularExpressionValidator ID="RegularExpressionValidator" runat="server" Display="Dynamic" ControlToValidate="bookidTextBox" ValidationExpression="^([\S\s]{13,13})$" ErrorMessage="Invalid ID/ISBN. Please try again" ValidationGroup="InsertBook">
        </asp:RegularExpressionValidator>
        <br />

        Title:
        <asp:TextBox ID="booktitleTextBox" runat="server" 
            Text='<%# Bind("booktitle") %>' />
        <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ErrorMessage="* Required" ControlToValidate="booktitleTextBox" ValidationGroup="InsertBook">
        </asp:RequiredFieldValidator>
        <br />

        Author's lastname:
        <asp:TextBox ID="lastnameTextBox" runat="server" 
            Text='<%# Bind("lastname") %>' />
        <asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" ErrorMessage="* Required" ControlToValidate="lastnameTextBox" ValidationGroup="InsertBook">
        </asp:RequiredFieldValidator>
        <br />

        Author's firstname:
        <asp:TextBox ID="firstnameTextBox" runat="server" 
            Text='<%# Bind("firstname") %>' />
        <asp:RequiredFieldValidator ID="RequiredFieldValidator4" runat="server" ErrorMessage="* Required" ControlToValidate="firstnameTextBox" ValidationGroup="InsertBook">
        </asp:RequiredFieldValidator>
        <br />

        Description:
        <asp:TextBox ID="descriptionTextBox" runat="server" 
            Text='<%# Bind("description") %>' />
        <asp:RequiredFieldValidator ID="RequiredFieldValidator5" runat="server" ErrorMessage="* Required" ControlToValidate="descriptionTextBox" ValidationGroup="InsertBook">
        </asp:RequiredFieldValidator>
        <br />

        Category:
        <asp:DropDownList ID="DropDownList1" runat="server" 
            DataSourceID="categoryDataSource" DataTextField="name" 
            DataValueField="categoryid" SelectedValue='<%# Bind("categoryid", "{0}") %>'>
        </asp:DropDownList>

        <asp:SqlDataSource ID="categoryDataSource" runat="server" 
            ConnectionString="<%$ ConnectionStrings:LibrarySystemConnectionString %>" 
            SelectCommand="SELECT [categoryid], [name] FROM [TblCategory]">
        </asp:SqlDataSource>
        <br />

        Date added:
        <asp:TextBox ID="dateaddedTextBox" runat="server" 
            Text='<%# Bind("dateadded") %>'/>
        <asp:RequiredFieldValidator ID="RequiredFieldValidator6" runat="server" ErrorMessage="* Required" ControlToValidate="dateaddedTextBox" ValidationGroup="InsertBook">
        </asp:RequiredFieldValidator>
        <%--<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server"
        ControlToValidate="dateaddedTextBox" ErrorMessage="RegularExpressionValidator"
        ValidationExpression="(19|20)\d\d(0[1-9]|1[012])(0[1-9]|[12][0-9]|3[01])">
        </asp:RegularExpressionValidator>--%>
        <br />

        Status:
        <asp:DropDownList ID="DropDownList2" runat="server" 
            DataSourceID="statusDataSource" DataTextField="statusname" 
            DataValueField="statusid" SelectedValue='<%# Bind("statusid", "{0}") %>'>
        </asp:DropDownList>

        <asp:SqlDataSource ID="statusDataSource" runat="server" 
            ConnectionString="<%$ ConnectionStrings:LibrarySystemConnectionString %>" 
            SelectCommand="SELECT [statusid], [statusname] FROM [BookStatus]">
        </asp:SqlDataSource>
        <br />

        Quantity:
        <asp:TextBox ID="quantityTextBox" runat="server" 
            Text='<%# Bind("quantity") %>' />
        <asp:RequiredFieldValidator ID="RequiredFieldValidator7" runat="server" ErrorMessage="* Required" ControlToValidate="quantityTextBox" ValidationGroup="InsertBook">
        </asp:RequiredFieldValidator>
        <br />

        <asp:Button ID="InsertButton" runat="server" CausesValidation="True" CommandName="Insert" Text="Add" ValidationGroup="InsertBook"/>

        <asp:Button ID="InsertCancelButton" runat="server" 
            CausesValidation="False" CommandName="Cancel" Text="Cancel" />

    </InsertItemTemplate>

    <ItemTemplate>
        <asp:LinkButton ID="NewButton" runat="server" CausesValidation="False" 
            CommandName="New" Text="New" />
    </ItemTemplate>
    <EmptyDataTemplate>
        <asp:LinkButton ID="NewButton" runat="server" CausesValidation="False" 
            CommandName="New" Text="New" />
    </EmptyDataTemplate>
    <HeaderTemplate>
        Add a new book
    </HeaderTemplate>

</asp:FormView>

Answer 1

您可以查看ItemInserting方法。

类似的东西：

void FormViewName_ItemInserting(object sender, FormViewInsertEventArgs e)
{
  string somevalue = e.Values["somefieldtoget"];
  //make your calls to the DB to check the somevalue doesn't exist 

  if(exists)
    e.Cancel = true; 
}

您也可以在数据源Inserting方法（假定sql数据源）上执行此操作....

void datasourcename_Inserting(object sender, SqlDataSourceCommandEventArgs e)
{
...
}

@ steve-wellens提到的另一种方法是，如果你有一个基于表单视图中的一个或多个字段的主键（不是自动生成的数字，那么下面的内容对于捕获插入的尝试非常有用）重复的密钥/记录。

void FormViewName_ItemInserted(object sender, FormViewInsertedEventArgs e)
{
  if (e.Exception != null)
  {
   if (((SqlException)e.Exception).Number == 2627)
   {
    e.ExceptionHandled = true;
    e.KeepInInsertMode = true;
    // Display error message.
   }
  }
}

Answer 2

最好在表上放置一个唯一索引，并捕获尝试插入重复记录时发生的异常。

这是确保诚信的最简单方法。否则，您必须启动一个读取事务来处理在您检查的时间和插入的时间之间的情况，其他一些过程正在做同样的事情。

Formview：当用户尝试插入数据时检查记录是否存在ASP.NET C＃

管理图书

2 个答案: