一起学~ASP.NET应用：DataSet 和XML（1）

数据集概述
概述：数据集即是内存当中的数据库。把实际数据库当中的一部分数据读到内存当中，并且以数据集形式存在。
分类：类型化（dataset派生的 可以直接通过名称引用表和列）和非类型化（需要通过tables集合引用列 一般我们用非类型化的）
实例：

//创建数据集和数据表
         protected void btnCreate_Click(object sender, System.EventArgs e)
        {
            DataSet dsUntyped = new DataSet("myDS");//创建数据集 非类型化的数据集
             DataTable dtMaster = new DataTable("Master");//创建数据表
             DataTable dtChild = new DataTable("Child");
            dsUntyped.Tables.Add(dtMaster);//把数据表添加到数据集中
             dsUntyped.Tables.Add(dtChild);
            Session["ds"] = dsUntyped;
            
        }
        //添加列
        protected void btnAddColumn_Click(object sender, System.EventArgs e)
        {
            DataSet dsUntyped = (DataSet)Session["ds"];
            dsUntyped.Tables["Master"].Columns.Add("MasterID",typeof(int));
            dsUntyped.Tables["Master"].Columns.Add("MasterValue",typeof(string));
            dsUntyped.Tables["Child"].Columns.Add("MasterLink",typeof(int));
            dsUntyped.Tables["Child"].Columns.Add("ChildID",typeof(int));
            dsUntyped.Tables["Child"].Columns .Add("ChildValue",typeof(string));
            //修改表头
            dsUntyped.Tables["Master"].Columns["MasterID"].Caption = "主ID";
            dsUntyped.Tables["Master"].Columns["MasterValue"].Caption = "值";
            Session["ds"] = dsUntyped;
            Bind();
        }

        protected void btnAddRow_Click(object sender, System.EventArgs e)
        {
            try
            {
                DataSet dsUntyped = (DataSet)Session["ds"];
                //为Master表添加两行
                DataRow dr = dsUntyped.Tables["Master"].NewRow();
                dr["MasterID"] = 1;
                dr["MasterValue"] = "One";
                dsUntyped.Tables["Master"].Rows.Add(dr);
                dr = dsUntyped.Tables["Master"].NewRow();
                dr["MasterID"] = 2;
                dr["MasterValue"] = "Two";
                dsUntyped.Tables["Master"].Rows.Add(dr);
                //为child表添加1行
                dr = dsUntyped.Tables["Child"].NewRow();
                dr["MasterLink"] = 1;
                dr["ChildID"] = 1;
                dr["ChildValue"] = "ChildOne";
                dsUntyped.Tables["Child"].Rows.Add(dr);
                Session["ds"] = dsUntyped;
                Bind();
            }
            catch(Exception ee)
            {
                Response.Write(ee.Message);
            }
        
        }
        //添加唯一键
        protected void Button1_Click(object sender, System.EventArgs e)
        {
            DataSet dsUntyped = (DataSet)Session["ds"];
            System.Data.UniqueConstraint uc = new UniqueConstraint("unqi",dsUntyped.Tables["Master"].Columns["MasterID"]);
            dsUntyped.Tables["Master"].Constraints.Add(uc);
            Session["ds"] = dsUntyped;
        }
        private void Bind()
        {
            DataSet dsUntyped = (DataSet)Session["ds"];
            dgMaster.DataSource = dsUntyped.Tables["Master"].DefaultView;
            dgChild.DataSource = dsUntyped.Tables["Child"].DefaultView;
            this.DataBind();
        }
        //添加外键 建立关系两个表
        protected void btnAddForeign_Click(object sender, System.EventArgs e)
        {
            DataSet dsUntyped = (DataSet)Session["ds"];
            System.Data.ForeignKeyConstraint fc = new ForeignKeyConstraint("fc",dsUntyped.Tables["Master"].Columns["MasterID"],dsUntyped.Tables["Child"].Columns["MasterLink"]);
            dsUntyped.Tables["Child"].Constraints.Add(fc);
            Session["ds"] = dsUntyped;

        }
        //修改MasterID
        protected void btnUpdateMID_Click(object sender, System.EventArgs e)
        {
            DataSet dsUntyped = (DataSet)Session["ds"];
            dsUntyped.Tables["Master"].Rows[0]["MasterID"] = 4;
            Bind();
        }
        //求值
        protected void Button2_Click(object sender, System.EventArgs e)
        {
            DataSet dsUntyped = (DataSet)Session["ds"];
            int nIndexTb = int.Parse(ddlTable.SelectedItem.Value);
            int nIndexRow = int.Parse(tbRow.Text);
            int nIndexCol = int.Parse(tbCol.Text);
            object obj = dsUntyped.Tables[nIndexTb].Rows[nIndexRow][nIndexCol];
            tbResult.Text = obj.ToString();
            
        }
        //赋值
        protected void btnUpdateDs_Click(object sender, System.EventArgs e)
        {
            DataSet dsUntyped = (DataSet)Session["ds"];
            int nIndexTb = int.Parse(ddlTable.SelectedItem.Value);
            int nIndexRow = int.Parse(tbRow.Text);
            int nIndexCol = int.Parse(tbCol.Text);
            dsUntyped.Tables[nIndexTb].Rows[nIndexRow][nIndexCol] = tbResult.Text;
            Session["ds"] = dsUntyped;
            Bind();
        }