LinQ 创建连接、简单增删改查

LinQ介绍

1、语言集成查询（Language Integrated Query）是一组用于c#和Visual Basic语言的扩展。它允许编写C#或者Visual Basic代码以查询数据库相同的方式操作内存数据。

2、LinQ与ADO.NET区别在于后台封装访问类代码量上减少

LINQ to SQL 建立实体类

使用LINQ to SQL设计器建立实体类：

第一步：

第二步：找到LinQ to Sql类

第三步：点击图片从左到右第一个加号，连接数据库

第四步：需要那个数据表，就鼠标把这个数据表拖到空白区域

属性拓展：

字段扩展：建一个部分类（关键字：partial）

public partial class users
{
    
    public string SexStr { get { return Convert.ToBoolean(_sex) ? "images/man.png" : "images/woman.png"; } }

    public string BirStr { get { return Convert.ToDateTime(this._birthday).ToString("yyyy年MM月dd日"); } }

    public string NationName
    {
        get
        {
            string end = "<暂无>";

            if (!String.IsNullOrEmpty(this._nation))
            {
                end = nation1.nationname;
            }

            return end;

        }
    }

    public string ClassName
    {
        get
        {
            return class1.classname;
        }
    }
  
}

LinQ的基本增删改查

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            //绑定数据库数据
            using (DataClassesDataContext con = new DataClassesDataContext())
            {
                Repeater1.DataSource = con.users.ToList();
                Repeater1.DataBind();
            }
        }
        Button1.Click += Button1_Click;
    }

    void Button1_Click(object sender, EventArgs e)
    {
        //查询你输入的内容，返回数据库该数据
        using (DataClassesDataContext con = new DataClassesDataContext())
        {
            List<users> list = con.users.ToList();

            if (TextBox1.Text != "")
            {
                List<users> list1 = con.users.Where(r => r.nickname.Contains(TextBox1.Text)).ToList();

                list = list.Intersect(list1).ToList();
            }
            if (TextBox2.Text != "")
            {
                List<users> list1 = con.users.Where(r => Convert.ToDateTime(r.birthday).Year == Convert.ToInt32(TextBox2.Text)).ToList();

                list = list.Intersect(list1).ToList();
            }
            if (TextBox3.Text != "")
            {
                List<users> list1 = con.users.Where(r => r.nation.Contains(TextBox3.Text)).ToList();

                list = list.Intersect(list1).ToList();
            }

            Repeater1.DataSource = list;
            Repeater1.DataBind();

        }
    }
}

public partial class Insert : System.Web.UI.Page
{
    
        protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            using (DataClassesDataContext con = new DataClassesDataContext())
            {
                DropDownList1.DataSource = con.nation.ToList();
                DropDownList1.DataTextField = "NationName";
                DropDownList1.DataValueField = "nationcode";
                DropDownList1.DataBind();
                DropDownList2.DataSource = con.@class.ToList();
                DropDownList2.DataTextField = "ClassName";
                DropDownList2.DataValueField = "classcode";
                DropDownList2.DataBind();
            }
        }
        Button1.Click += Button1_Click;
    }

    void Button1_Click(object sender, EventArgs e)
    {
        users u = new users();
        u.usersname = TextBox1.Text;
        u.password = TextBox2.Text;
        u.nickname = TextBox3.Text;
        if (Convert.ToBoolean(u.sex))
            RadioButton1.Checked = true;
        else
            RadioButton2.Checked = true;
        u.birthday = Convert.ToDateTime(TextBox4.Text);
        u.nation = DropDownList1.SelectedValue;
        u.@class = DropDownList2.SelectedValue;

        try
        {

            using (DataClassesDataContext con = new DataClassesDataContext())
            {
                con.users.InsertOnSubmit(u);
                con.SubmitChanges();
                Response.Write("<script>");
                Response.Write("alert('添加成功！');");
                Response.Write("window.location.href='Default.aspx';");
                Response.Write("</script>");
            }
        }
        catch
        {
            Response.Write("<script>");
            Response.Write("alert('添加失败！');");
            Response.Write("</script>");
        }

    }
}

public partial class Delete : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            string un = Request["i"];
            using (DataClassesDataContext con = new DataClassesDataContext())
            {
                users u = con.users.Where(r => r.usersname == un).FirstOrDefault();
                if (u != null)
                {
                    con.users.DeleteOnSubmit(u);
                    con.SubmitChanges();
                }
            }

            Response.Redirect("Default.aspx");
        }
    }
}

public partial class Update : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            using (DataClassesDataContext con = new DataClassesDataContext())
            {
                DropDownList1.DataSource = con.nation.ToList();
                DropDownList1.DataTextField = "NationName";
                DropDownList1.DataValueField = "nationcode";
                DropDownList1.DataBind();
                DropDownList2.DataSource = con.@class.ToList();
                DropDownList2.DataTextField = "ClassName";
                DropDownList2.DataValueField = "classcode";
                DropDownList2.DataBind();
            }
            string un = Request["i"];
            if (String.IsNullOrEmpty(un))
            {

            }

            using (DataClassesDataContext con = new DataClassesDataContext())
            {
                users u = con.users.Where(r => r.usersname == un).FirstOrDefault();
                if (u == null)
                {

                }
                TextBox1.Text = u.usersname;
                TextBox2.Text = u.password;
                TextBox3.Text = u.nickname;
                if (Convert.ToBoolean(u.sex))
                    RadioButton1.Checked = true;
                else
                    RadioButton2.Checked = true;
                TextBox4.Text = u.birthday.ToString();
                DropDownList1.SelectedValue = u.nation;
                DropDownList2.SelectedValue = u.@class;
            }
        }

        Button1.Click += Button1_Click;
    }

    void Button1_Click(object sender, EventArgs e)
    {
        using (DataClassesDataContext con = new DataClassesDataContext())
        {
            users u = con.users.Where(r => r.usersname == TextBox1.Text.Trim()).FirstOrDefault();

            u.password = TextBox2.Text;
            u.nickname = TextBox3.Text;
            if (RadioButton1.Checked)
                u.sex = true;
            else
                u.sex = false;
             u.birthday = Convert.ToDateTime(TextBox4.Text);
            u.nation = DropDownList1.SelectedValue;
            u.@class = DropDownList2.SelectedValue;

            con.SubmitChanges();
            Response.Redirect("Default.aspx");

        }
    }
}