窗体视图:当用户尝试 ASP.NET C# 插入数据时检查记录是否存在
本文关键字：数据 插入 检查 记录 存在 是否 NET 视图 用户 ASP 窗体 | 更新日期: 2023-09-27 17:55:29
如果用户单击插入链接按钮后数据库中存在记录，我有没有办法生成消息框？我希望表单视图检查记录是否存在，如果不进行插入。
帮助将不胜感激。提前致谢:)
这是我的代码示例：
管理图书
添加/删除书籍注意：有关书籍 ID/ISBN，请参阅国际标准书号中的条形码，通常位于 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" />
<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>
您可以签入 ItemInserting 方法。
像这样：
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;
}
您也可以在数据源插入方法（假定为 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，如果您的主键基于表单视图中的一个或多个字段（不是自动生成的数字），那么下面的主键将非常适合捕获插入重复键/记录的尝试。
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.
}
}
}
最好在
表上放置一个唯一的索引，并捕获尝试插入重复记录时发生的异常。
这是确保完整性的最简单方法。 否则，您必须启动读取事务来处理在检查和插入之间，其他进程正在执行完全相同的事情的情况。