LINQ - SQL CRUD

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无论无涯教程如何处理对象(如添加、删除或更新对象集合中的项)，LINQ to SQL都具有维护更改的功能，直到使用方法SubmitChanges()提交更改。提交更改后，LINQ to SQL会将操作转换为SQL，并将更改提交到数据库。

LINQ to SQL INSERT/UPDATE和DELETE的语法

以下是在LINQ to SQL中使用的Insert/Update或Delete操作的语法。

链接：https://www.learnfk.comhttps://www.learnfk.com/linq/linq-to-sql-crud-operations.html

来源：LearnFk无涯教程网

插入操作

以下是在C#中使用LINQ to SQL INSERT操作查询在数据库中插入数据的语法。

复制代码
EmployeeDBDataContext db = new EmployeeDBDataContext();
EmployeeDetail emp = new EmployeeDetail();
emp.EmpName = txtname.Text;
emp.Location = txtlocation.Text;
db.EmployeeDetails.InsertOnSubmit(emp);
db.SubmitChanges();

更新操作

以下是使用LINQ to SQL UPDATE操作查询更新数据库中数据的语法。

复制代码
EmployeeDBDataContext db = new EmployeeDBDataContext();
EmployeeDetail emp = new EmployeeDetail();
emp = db.EmployeeDetails.Single(x => x.EmpId == empid);
emp.EmpName = txtname.Text;
emp.Location = txtlocation.Text;
emp.Gender = txtgender.Text;
db.SubmitChanges();

删除操作

下面是在C#中使用LINQ to SQL删除操作删除数据库中数据的语法。

复制代码
EmployeeDBDataContext db = new EmployeeDBDataContext();
EmployeeDetail emp = new EmployeeDetail();
emp = db.EmployeeDetails.Single(x => x.EmpId == empid);
db.EmployeeDetails.DeleteOnSubmit(emp);
db.SubmitChanges();

插入、更新、删除操作

在开始实现LINQ to SQL INSERT、UPDATE和DELETE操作之前，首先需要创建一个包含所需表的数据库，并将这些表映射到LINQ to SQL文件(.dbml)。

一旦创建了所需的表并将其映射到.dbml文件。现在，希望显示应用程序中的数据。为此，无涯教程右键单击application->Select Add->New Item-> Select web Form->将名称指定为Default.aspx，然后单击OK按钮。

现在打开Default.aspx页面并编写代码，如下所示：

复制代码
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
        
            <div class="GridviewDiv">

<asp:GridView runat="server" ID="gvDetails" ShowFooter="true" AllowPaging="true" PageSize="10" AutoGenerateColumns="false" DataKeyNames="Id,Name" OnPageIndexChanging="gvDetails_PageIndexChanging" OnRowCancelingEdit="gvDetails_RowCancelingEdit"

OnRowEditing="gvDetails_RowEditing" OnRowUpdating="gvDetails_RowUpdating" OnRowDeleting="gvDetails_RowDeleting" OnRowCommand ="gvDetails_RowCommand" >

<HeaderStyle CssClass="headerstyle" />

<Columns>

<asp:BoundField DataField="Id" HeaderText="Id" ReadOnly="true" />

<asp:TemplateField HeaderText="Name">

<ItemTemplate>

<asp:Label ID="lblName" runat="server" Text='<%# Eval("Name")%>'/>

</ItemTemplate>

<EditItemTemplate>

<asp:TextBox ID="txtName" runat="server" Text='<%# Eval("Name")%>'/>

</EditItemTemplate>

<FooterTemplate>

<asp:TextBox ID="txtfName" runat="server" />

</FooterTemplate>

</asp:TemplateField>

<asp:TemplateField HeaderText = "Location">

<ItemTemplate>

<asp:Label ID="lblLocation" runat="server" Text='<%# Eval("Location")%>'></asp:Label>

</ItemTemplate>

<EditItemTemplate>

<asp:TextBox ID="txtLocation" runat="server" Text='<%# Eval("Location")%>'/>

</EditItemTemplate>

<FooterTemplate>

<asp:TextBox ID="txtfLocation" runat="server" />

</FooterTemplate>

</asp:TemplateField>

<asp:TemplateField HeaderText="Gender">

<ItemTemplate>

<asp:Label ID="lblGender" runat="server" Text='<%# Eval("Gender")%>'/>

</ItemTemplate>

<EditItemTemplate>

<asp:TextBox ID="txtGender" runat="server" Text='<%# Eval("Gender")%>'/>

</EditItemTemplate>

<FooterTemplate>

<asp:TextBox ID="txtfGender" runat="server" />

<asp:Button ID="btnAdd" CommandName="AddNew" runat="server" Text="Add" />

</FooterTemplate>

</asp:TemplateField>

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

</Columns>

</asp:GridView>

<asp:Label ID="lblresult" runat="server"></asp:Label>
        </div>
    </form>
</body>
</html>

现在打开文件后面的代码并编写代码，如下所示：

复制代码
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
{
    EmployeeDataContext db = new EmployeeDataContext();
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)

        {

            BindGridview();

        }
    }
    protected void BindGridview()

    {

        var result = from ed in db.EmployeeDetails

                     select new

                     {

                         Id = ed.Id,

                         Name = ed.Name,

                         Location = ed.Location,

                         Gender = ed.Gender

                     };

        gvDetails.DataSource = result;

        gvDetails.DataBind();

    }
    protected void gvDetails_RowCommand(object sender, GridViewCommandEventArgs e)

    {

        if (e.CommandName.Equals("AddNew"))

        {

            TextBox txtname = (TextBox)gvDetails.FooterRow.FindControl("txtfName");

            TextBox txtlocation = (TextBox)gvDetails.FooterRow.FindControl("txtfLocation");

            TextBox txtgender = (TextBox)gvDetails.FooterRow.FindControl("txtfGender");

            EmployeeDetail emp = new EmployeeDetail();

            emp.Name = txtname.Text;

            emp.Location = txtlocation.Text;

            emp.Gender = txtgender.Text;

            db.EmployeeDetails.InsertOnSubmit(emp);

            db.SubmitChanges();

            lblresult.ForeColor = Color.Green;

            lblresult.Text = txtname.Text + " details inserted successfully";

            BindGridview();

        }

    }
    protected void gvDetails_RowEditing(object sender, GridViewEditEventArgs e)

    {

        gvDetails.EditIndex = e.NewEditIndex;

        BindGridview();

    }

    protected void gvDetails_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)

    {

        gvDetails.EditIndex = -1;

        BindGridview();

    }

    protected void gvDetails_PageIndexChanging(object sender, GridViewPageEventArgs e)

    {

        gvDetails.PageIndex = e.NewPageIndex;

        BindGridview();


    }
    protected void gvDetails_RowUpdating(object sender, GridViewUpdateEventArgs e)

    {

        int empid = Convert.ToInt32(gvDetails.DataKeys[e.RowIndex].Values["Id"].ToString());

        TextBox txtname = (TextBox)gvDetails.Rows[e.RowIndex].FindControl("txtName");

        TextBox txtlocation = (TextBox)gvDetails.Rows[e.RowIndex].FindControl("txtLocation");

        TextBox txtgender = (TextBox)gvDetails.Rows[e.RowIndex].FindControl("txtGender");

        EmployeeDetail emp = new EmployeeDetail();

        emp = db.EmployeeDetails.Single(x => x.Id == empid);

        emp.Name = txtname.Text;

        emp.Location = txtlocation.Text;

        emp.Gender = txtgender.Text;

        db.SubmitChanges();



        gvDetails.EditIndex = -1;

        BindGridview();

        lblresult.ForeColor = Color.Green;

        lblresult.Text = txtname.Text + " details updated successfully";
    }
    protected void gvDetails_RowDeleting(object sender, GridViewDeleteEventArgs e)

    {

        int empid = Convert.ToInt32(gvDetails.DataKeys[e.RowIndex].Values["Id"].ToString());

        string empname = gvDetails.DataKeys[e.RowIndex].Values["Name"].ToString();

        EmployeeDetail emp = new EmployeeDetail();

        emp = db.EmployeeDetails.Single(x => x.Id == empid);

        db.EmployeeDetails.DeleteOnSubmit(emp);

        db.SubmitChanges();

        BindGridview();

        lblresult.ForeColor = Color.Green;

        lblresult.Text = empname + " details deleted successfully";

    }
}

在上面的示例中，实现了LINQ to SQL SELECT、INSERT以及UPDATE、DELETE操作。现在无涯教程将运行应用程序并查看结果。

无涯教程网

LINQ Crud

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