c#实现两个(DataTable)数据合并

在C#代码中，要将这两个表拼接起来，也有很多比较“笨”的办法，就是例如循环获取数据一条条拼起来，此办法在数据量少、字段少的可以使用此办法，但在数据量大的情况下会影响性能，而且字段多的时候也需要写一大堆给每个字段依次赋值的代码，性能就有所下降，下列将介绍合并DataTable的几种方法

主要介绍三种方案

方案一【For循环+RowFilter】

dt_All.Rows.Clear();
dgvResult.DataSource = dt_All;
//方案一：For循环
for (int i = 0; i < dt_Head.Rows.Count; i++)
{
DataRow drAll = dt_All.NewRow();
drAll["StockID"] = dt_Head.Rows[i]["StockID"];
drAll["ProductName"] = dt_Head.Rows[i]["ProductName"];
DataView dv = new DataView(dt_Detail);
dv.RowFilter = string.Format("StockID = '{0}'", dt_Head.Rows[i]["StockID"]);
DataTable dtDetail = dv.ToTable();
if (dtDetail.Rows.Count > 0)
{
drAll["Num"] = dtDetail.Rows[0]["Num"];
drAll["Money"] = dtDetail.Rows[0]["Money"];
}
dt_All.Rows.Add(drAll);
}
dgvResult.DataSource = dt_All;

方案二【适合字段比较少的情况下。】

dt_All.Rows.Clear();
dgvResult.DataSource = dt_All;
//方案二：字段少的情况下
var Little = from rHead in dt_Head.AsEnumerable()
from rDetail in dt_Detail.AsEnumerable()
where rHead.Field<int>("StockID") == rDetail.Field<int>("StockID")
select new
{
StockID = rHead.Field<int>("StockID"),
ProductName = rHead.Field<string>("ProductName"),
Num = rDetail.Field<int>("Num"),
Money = rDetail.Field<decimal>("Money"),
};
DataTable dtNew = dt_All.Copy();
foreach (var obj in Little)
{
dtNew.Rows.Add(obj.StockID, obj.ProductName, obj.Num, obj.Money);
}
dgvResult.DataSource = dtNew;

方案三【LINQ提供了与SQL类型的JOIN类似的方法，并且字段比较多的情况下，可使用如下方式。】

dt_All.Rows.Clear();
dgvResult.DataSource = dt_All;
//方案三：字段多的情况下
var query =
from rHead in dt_Head.AsEnumerable()
join rDetail in dt_Detail.AsEnumerable()
on rHead.Field<Int32>("StockID") equals rDetail.Field<Int32>("StockID")
select rHead.ItemArray.Concat(rDetail.ItemArray.Skip(1));

foreach (var obj in query)
{
DataRow dr = dt_All.NewRow();
dr.ItemArray = obj.ToArray();
dt_All.Rows.Add(dr);
}
dgvResult.DataSource = dt_All;

使用Concat将表1和表2的字段拼接起来，作为总表dt_All的字段，但由于表1、表2中都存在字段StockID，不能在表中出现重复的字段，因此使用Skip(1)跳过表2中的第一个字段StockID。

完整代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
public partial class FrmDemo : Form
{
DataTable dt_Head = new DataTable();
DataTable dt_Detail = new DataTable();
DataTable dt_All = new DataTable();
public FrmDemo()
{
InitializeComponent();
InitData();
}

private void InitData()
{
dt_Head.Columns.Add("StockID", typeof(Int32));
dt_Head.Columns.Add("ProductName", typeof(String));

dt_Detail.Columns.Add("StockID", typeof(Int32));
dt_Detail.Columns.Add("Num", typeof(Int32));
dt_Detail.Columns.Add("Money", typeof(decimal));

dt_All.Columns.Add("StockID", typeof(Int32));
dt_All.Columns.Add("ProductName", typeof(String));
dt_All.Columns.Add("Num", typeof(Int32));
dt_All.Columns.Add("Money", typeof(decimal));

for (int i = 1; i < 10; i++)
{
DataRow dr_Head = dt_Head.NewRow();
DataRow dr_Detail = dt_Detail.NewRow();
dr_Head["StockID"] = i;
dr_Head["ProductName"] = "商品" + i;

dr_Detail["StockID"] = i;
dr_Detail["Num"] = i;
dr_Detail["Money"] = i * 0.5;

dt_Head.Rows.Add(dr_Head);
dt_Detail.Rows.Add(dr_Detail);
}
}

private void btnFor_Click(object sender, EventArgs e)
{
dt_All.Rows.Clear();
dgvResult.DataSource = dt_All;
//方案一：For循环
for (int i = 0; i < dt_Head.Rows.Count; i++)
{
DataRow drAll = dt_All.NewRow();
drAll["StockID"] = dt_Head.Rows[i]["StockID"];
drAll["ProductName"] = dt_Head.Rows[i]["ProductName"];
DataView dv = new DataView(dt_Detail);
dv.RowFilter = string.Format("StockID = '{0}'", dt_Head.Rows[i]["StockID"]);
DataTable dtDetail = dv.ToTable();
if (dtDetail.Rows.Count > 0)
{
drAll["Num"] = dtDetail.Rows[0]["Num"];
drAll["Money"] = dtDetail.Rows[0]["Money"];
}
dt_All.Rows.Add(drAll);
}
dgvResult.DataSource = dt_All;
}

private void btnLittle_Click(object sender, EventArgs e)
{
dt_All.Rows.Clear();
dgvResult.DataSource = dt_All;
//方案二：字段少的情况下
var Little = from rHead in dt_Head.AsEnumerable()
from rDetail in dt_Detail.AsEnumerable()
where rHead.Field<int>("StockID") == rDetail.Field<int>("StockID")
select new
{
StockID = rHead.Field<int>("StockID"),
ProductName = rHead.Field<string>("ProductName"),
Num = rDetail.Field<int>("Num"),
Money = rDetail.Field<decimal>("Money"),
};
DataTable dtNew = dt_All.Copy();
foreach (var obj in Little)
{
dtNew.Rows.Add(obj.StockID, obj.ProductName, obj.Num, obj.Money);
}
dgvResult.DataSource = dtNew;
}

private void btnMore_Click(object sender, EventArgs e)
{
dt_All.Rows.Clear();
dgvResult.DataSource = dt_All;
//方案三：字段多的情况下
var query =
from rHead in dt_Head.AsEnumerable()
join rDetail in dt_Detail.AsEnumerable()
on rHead.Field<Int32>("StockID") equals rDetail.Field<Int32>("StockID")
select rHead.ItemArray.Concat(rDetail.ItemArray.Skip(1));

foreach (var obj in query)
{
DataRow dr = dt_All.NewRow();
dr.ItemArray = obj.ToArray();
dt_All.Rows.Add(dr);
}
dgvResult.DataSource = dt_All;
}

private void btnClear_Click(object sender, EventArgs e)
{
dt_All.Rows.Clear();
dgvResult.DataSource = dt_All;
}
}
}