个人感觉Linq实用灵活性很大，参考一篇大牛的文章LINQ查询返回DataTable类型
http://xuzhihong1987.blog.163.com/blog/static/26731587201101853740294/
附上自己写的一个测试程序源代码。
//创建自定义DataTable
String[] _sFiled = new String[] { "ID", "PC", "EPC", "CRC", "RSSI", "FREQANT", "INVCOUNT" };
# region Linq写法
// LinQ写法1：
//var numbers_1 = from number in numbers where (number % 2 == 0) orderby number descending select number;//orderby number descending 这是对筛选出来的数值进行排序
// foreach (var i in numbers_1)
// {
// Console.WriteLine(i);
// }
//LinQ写法2：
// var numbers_1 = numbers.Where(i => i % 2 == 0).Select(i => i);//输出用写法1一样
#endregion DataTable _dtAudit = CreateSelfDataTable(_sFiled); _dtAudit.Rows.Add("a1", "b1", "c1","","","","");
_dtAudit.Rows.Add("a1", "b2", "c2", "", "", "", "");
_dtAudit.Rows.Add("a2", "b3", "c3", "", "", "", "");
_dtAudit.Rows.Add("a3", "b4", "c4", "", "", "", "");
_dtAudit.Rows.Add("a1", "b5", "c5", "", "", "", "");
_dtAudit.Rows.Add("a2", "b6", "c6", "", "", "", ""); var query1 = (from contact in _dtAudit.AsEnumerable() //查询
orderby contact.Field<string>("ID") descending //排序
group contact by contact.Field<string>("PC") into g //分组
select new {ID=g.FirstOrDefault().Field<string>("ID"),PC=g.FirstOrDefault().Field<string>("PC"),EPC=
g.FirstOrDefault().Field<string>("EPC"),CRC=g.FirstOrDefault().Field<string>("CRC"),RSSI=g.FirstOrDefault(
).Field<string>("RSSI")}).ToList();
DataTable contacts1 =ToDataTable(query1);
SetListView(listView1, contacts1);
} /// <summary>
/// 创建自定义列DataTable
/// </summary>
/// <param name="sList"></param>
/// <returns></returns>
public DataTable CreateSelfDataTable(String[] sList)
{
DataTable _dtSelf = new DataTable(); foreach (String s in sList)
{
_dtSelf.Columns.Add(s);
}
_dtSelf.AcceptChanges(); return _dtSelf;
} /// <summary>
/// 下面通过一个方法来实现返回DataTable类型
/// LINQ返回DataTable类型
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="varlist"></param>
/// <returns></returns>
public static DataTable ToDataTable<T>(IEnumerable<T> varlist)
{
DataTable dtReturn = new DataTable();
// column names
PropertyInfo[] oProps = null;
if (varlist == null)
return dtReturn;
foreach (T rec in varlist)
{
if (oProps == null)
{
oProps = ((Type)rec.GetType()).GetProperties();
foreach (PropertyInfo pi in oProps)
{
Type colType = pi.PropertyType;
if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition()
== typeof(Nullable<>)))
{
colType = colType.GetGenericArguments()[];
}
dtReturn.Columns.Add(new DataColumn(pi.Name, colType));
}
}
DataRow dr = dtReturn.NewRow();
foreach (PropertyInfo pi in oProps)
{
dr[pi.Name] = pi.GetValue(rec, null) == null ? DBNull.Value : pi.GetValue
(rec, null);
}
dtReturn.Rows.Add(dr);
}
return dtReturn;
} /// <summary>
/// 绑定ListView
/// </summary>
private void SetListView(System.Windows.Forms.ListView listView, DataTable dt)
{
if (listView.Items.Count > )
{
listView.Items.Clear();
}
if (dt != null && dt.Rows.Count > )
{
ListViewItem lv = null;
for (int i = ; i < dt.Rows.Count; i++)
{
lv = new ListViewItem(dt.Rows[i][].ToString()); //创建一列的多行对象
lv.Tag = dt.Rows[i][].ToString(); //该lv对象绑定多行一列值
for (int j = ; j < dt.Columns.Count; j++)
{
lv.SubItems.Add(dt.Rows[i][j].ToString()); //一行添加多列的值
}
listView.Items.Add(lv);
} }
}
LINQ基本语法及其示例
http://xuzhihong1987.blog.163.com/blog/static/26731587201111342756123/
说明：
1、在未作任何说明的情况下，以下用到的db变量都是DataContext的实例对象，声明语法类似如下：
using (BP_DataClassesDataContext db = new BP_DataClassesDataContext(ConnectionStrings.GetInstance("ZJ").Con))
{
//Code
}
2、默认q为Iqueryable类型变量
简单查询：
var q = from p in db.view_PreTestResultAuditList
select p;
简单条件查询：
方式一：直接使用where关键字
var q = from c in db.view_PrTestList
where c.FTestmanID.Equals(UserContext.CurrentUser.FID)
select c;
方式二：使用lambda 表达式
var q = db.TOriInfoAutoMemory.Where(c => c.FSampleName == sampleName);
使用 &&和|| 带代替And或Or关键字：
var entity = db.TSampleOriginalInfo.FirstOrDefault(c => c.FFromID.Equals(fromID) && c.FSampleID.Equals(sampleID));
like模糊条件查询：
//使用C#中的Contains关键字代替SQL中的like关键字
q = q.Where(c => c.FTaskCode.Contains(condition.Name));
In包含查询：
/// <param name="certificateIDs"> string[] </param>
var certi = (from c in db.TMSCertificate
where certificateIDs.ToList().Contains(c.FID.ToString())
select c).ToList();
等价于：select * from TMSCertificate where FID in /* certificateIDs */
Skip和Take实现分页查询：
var q = from c in db.view_PrTestList
where c.FTestmanID.Equals(UserContext.CurrentUser.FID)
select c;
twi.data = (q.Skip(paging.startIndex).Take(paging.pageSize)).ToList();
//其中startIndex：跳过的系列中指定的条数
// pageSize：每页显示条数（记录数）
Distinct方法去除重复：
var p = (from c in dc.TSampleOriginalInfo
where sampleIDs.Contains(c.FSampleID.ToString())
select new
{
c.FFromID,
c.FName
}).Distinct();
查询指定列使new构造集合：
var p = (from c in dc.TSampleOriginalInfo
where sampleIDs.Contains(c.FSampleID.ToString())
select new
{
c.FFromID,
c.FName
}).Distinct();
join连接查询：详见下面的【join查询实例】
//此处省略……
FirstOrDefault查询满足条件的第一条记录或不存在是返回null，不发生异常：
foreach (var fromID in fromIDs)
{
var entity = db.TSampleOriginalInfo.FirstOrDefault(c => c.FFromID.Equals(fromID) && c.FSampleID.Equals(sampleID));
if (entity != null)
{
entities.Add(entity);
}
}
LINQ to SQL 的重要方法：SubmitChanges方法：
无论您对对象做了多少项更改，都只是在更改内存中的副本。您并未对数据库中的实际数据做任何更改。直到您对 DataContext 显式调用 SubmitChanges方法，您所做的更改才会传输到服务器。
db.SubmitChanges();
新增/删除/修改后都需要显式的调用该方法！
以下是示例代码
/// <summary>
/// 添加
/// </summary>
/// <param name="varCustomer">要添加的对象</param>
/// <returns></returns>
public bool New(TTrademark idc)
{
using (CP_DataClassesDataContext db = new CP_DataClassesDataContext(GS.MODEL.ConnectionStrings.GetInstance("ZJ").Con))
{
if (idc != null)
{
db.TTrademark.InsertOnSubmit(idc);
db.SubmitChanges();
return true;
}
else
{
return false;
}
}
}
/// <summary>
/// 新增多个【使用InsertAllOnSubmit】
/// </summary>
/// <param name="model"></param>
public void New(GS.MODEL.TItem model)
{
using (CP_DataClassesDataContext db = new CP_DataClassesDataContext(GS.MODEL.ConnectionStrings.GetInstance("ZJ").Con))
{
List<GS.MODEL.TItem> entities = new List<GS.MODEL.TItem>();
GS.MODEL.TItem entity = new GS.MODEL.TItem()
{
FID = Guid.NewGuid(),
FName =model.FName ,
FParentName = model.FParentName,
FFastCode = model.FFastCode,
FRemark=model.FRemark,
FSort=model.FSort
};
entities.Add(entity);
db.TItem.InsertAllOnSubmit(entities);
db.SubmitChanges();
}
}
/// <summary>
/// 修改
/// </summary>
/// <param name="model"></param>
public void Edit(GS.MODEL.TItem model)
{
using(CP_DataClassesDataContext db=new CP_DataClassesDataContext(GS.MODEL.ConnectionStrings.GetInstance("ZJ").Con))
{
GS.MODEL.TItem items = db.TItem.Single(c => c.FID == model.FID);
items.FName = model.FName;
items.FParentName = model.FParentName;
items.FRemark = model.FRemark;
items.FSort = model.FSort;
items.FFastCode = model.FFastCode;
db.SubmitChanges();
}
}
/// <summary>
/// 删除
/// </summary>
/// <param name="IDs"></param>
public void Delete(string[] ids)
{
using (CP_DataClassesDataContext db = new CP_DataClassesDataContext(GS.MODEL.ConnectionStrings.GetInstance("ZJ").Con))
{
List<GS.MODEL.TItem> entities = new List<GS.MODEL.TItem>();
foreach (var id in ids)
{
var entity = db.TItem.FirstOrDefault(c => c.FID.Equals(id));
if (entity != null)
{
entities.Add(entity);
}
}
db.TItem.DeleteAllOnSubmit(entities);
db.SubmitChanges();
}
}
/// <summary>
/// 【简单查询】获取指定计量标准考核证书下的计量标准器/检定规程/主要配套设备
/// </summary>
/// <param name="certifiacteID"></param>
/// <returns></returns>
public IList<view_CertificateOriginalInfo> GetViewByCertificateID(Guid certifiacteID)
{
using (BPDataContext db = new BPDataContext(TCTC_ConnectionStrings.connStrJL))
{
var d = from c in db.view_CertificateOriginalInfo
where c.FCertificateID == certifiacteID
select c;
return d.ToList();
}
}
/// <summary>
/// 【综合查询】我的待检测结果任务单
/// </summary>
/// <param name="paging"></param>
/// <param name="condition"></param>
/// <returns></returns>
public TwiReturn GetMyWorkList(PagingCondition paging, ConditionModel condition)
{
TwiReturn twi = new TwiReturn();
using (BP_DataClassesDataContext db = new BP_DataClassesDataContext(ConnectionStrings.GetInstance("ZJ").Con))
{
var q = from c in db.view_PrTestList
where c.FTestmanID.Equals(UserContext.CurrentUser.FID)
select c;
if (condition != null)
{
if (condition.NameSign == "TaskCode" && condition.Name != "")
{
q = q.Where(c => c.FTaskCode.Contains(condition.Name));
}
else if (condition.NameSign == "TestItemName" && condition.Name != "")
{
q = q.Where(c => c.FTestItemName.Contains(condition.Name));
}
}
twi.totalCount = q.Count();
if (paging.needPaging)
{
twi.data = (q.Skip(paging.startIndex).Take(paging.pageSize)).ToList();
}
else
{
twi.data = q.ToList();
}
return twi;
}
}
/// <summary>
/// 选择计量标准考核证书
/// </summary>
/// <param name="sampleIDs"></param>
/// <param name="certificateIDs"></param>
public void SelectCertificate(string[] sampleIDs, string[] certificateIDs)
{
BPDataContext bpDC = new BPDataContext(TCTC_ConnectionStrings.connStrJL);
CPDataContext cpDc = new CPDataContext(TCTC_ConnectionStrings.connStrJL);
var certi = (from c in cpDc.TMSCertificate
where certificateIDs.ToList().Contains(c.FID.ToString())
select c).ToList();
List<TSampleOriginalInfo> entities = new List<TSampleOriginalInfo>();
foreach (var sampleID in sampleIDs)
{
foreach (var c in certi)
{
TSampleOriginalInfo entity = new TSampleOriginalInfo()
{
FID = Guid.NewGuid(),
FFromID = c.FID,
FType = ,
FSampleID = new Guid(sampleID),
FName = c.FCertificateName,
FCode = c.FCode,
FRange = c.FMeasurementRange,
FUncertainty = c.FLevel,
FCertificateNo = c.FCode,//c.FNumber,zjw修改
FValidDateTo = c.FPeriodDate
};
entities.Add(entity);
}
}
bpDC.TSampleOriginalInfo.InsertAllOnSubmit(entities);
bpDC.SubmitChanges();
bpDC.Dispose();
cpDc.Dispose();
}
/// <summary>
/// 获取样品之标准/计量标准器/主要配套设备/检定规程
/// </summary>
/// <param name="sampleIDs"></param>
/// <returns></returns>
public DataTable GetBySampleIDs(List<string> sampleIDs)
{
using (BPDataContext dc = new BPDataContext(TCTC_ConnectionStrings.connStrJL))
{
var p = (from c in dc.TSampleOriginalInfo
where sampleIDs.Contains(c.FSampleID.ToString())
select new
{
c.FFromID,
c.FType,
c.FName,
c.FCode,
c.FRange,
c.FModel,
c.FUncertainty,
c.FCertificateNo,
c.FValidDateTo,
c.FManufacturer
}).Distinct();
return LinqToDataTable.ToDataTable(p.ToList());
}
}
/// <summary>
/// 【join查询实例】获取带检测的器具信息
/// </summary>
/// <returns></returns>
public DataTable GetBySampleName(string sampleName)
{
using (BPDataContext dc = new BPDataContext(TCTC_ConnectionStrings.connStrJL))
{
var sample = from c in dc.view_Sample_WithVCItem
where c.FEndTag == && c.FTaskEndTag == && c.FOutSourcingTag == && c.FAssignTag == && c.FTestCompleteTag == && c.FIsOuter == "否"
select c;
var r = from s in sample
join v in dc.view_GetSampleLeastOrginalRecord
on s.FID equals v.FSampleID into recs
from v in recs.DefaultIfEmpty()
join t in dc.TTask
on s.FTaskID equals t.FID into ts
from t in ts
where (sampleName == "" ? true : s.FName == sampleName) && (s.FReceiverID == UserContext.CurrentUser.FID || TCTC_ConnectionStrings.TestResultFilterByTester == "")
orderby s.FName, t.FCode, s.FCode
select new
{
SampleID = s.FID,
SampleCode = s.FCode,
s.FName,
s.FAnotherName,
s.FTaskID,
s.FIsRepair,
s.FIsNeedOriginalRecord,
s.FTestProperty,
s.FRepairTag,
s.VCItemID,
s.CertiID,
s.CertiName,
s.TechID,
s.TechName,
s.TechCode,
s.FReTestTag,
s.FReTestFromTag,
v.FNumber,
v.FFileName,
v.FCertificateNo,
v.FOriginalRecordID,
v.FTag,
TaskCode = t.FCode,
t.FRemark,
t.FIsUrgent,
s.FTaskType,
s.FTaskTypeID,
s.FMeasurementRange,
s.FLevel,
s.FSigPrice
};
DataTable dt = LinqToDataTable.ToDataTable(r.ToList());
return dt;
}
}