LINQ to DataSet的DataTable操作

1. DataTable读取列表DataSet ds = new DataSet();
// 省略ds的Fill代码
DataTable products = ds.Tables["Product"];
IEnumerable<DataRow> rows = from p in products.AsEnumerable()
select p;
foreach (DataRow row in rows)
{
Console.WriteLine(row.Field<string>("ProductName"));
}DataSet ds = new DataSet();
// 省略ds的Fill代码
DataTable products = ds.Tables["Product"];
var rows = products.AsEnumerable()
.Select(p => new
{
ProductID = p.Field<int>("ProductID"),
ProductName = p.Field<string>("ProductName"),
UnitPrice = p.Field<decimal>("UnitPrice")
});
foreach (var row in rows)
{
Console.WriteLine(row.ProductName);
}

var products = ds.Tables["Product"].AsEnumerable();
var query = from p in products
select p.Field<string>("ProductName");

2. DataTable查询

var rows = products.AsEnumerable()
.Where(p => p.Field<decimal>("UnitPrice") > 10m)
.Select(p => new
{
ProductID = p.Field<int>("ProductID"),
ProductName = p.Field<string>("ProductName"),
UnitPrice = p.Field<decimal>("UnitPrice")
});

3. DataTable数据排序

var rows = products.AsEnumerable()
.Where(p => p.Field<decimal>("UnitPrice") > 10m)
.OrderBy(p => p.Field<int>("SortOrder"))
.Select(p => new
{
ProductID = p.Field<int>("ProductID"),
ProductName = p.Field<string>("ProductName"),
UnitPrice = p.Field<decimal>("UnitPrice")
});var expr = from p in products.AsEnumerable()
orderby p.Field<int>("SortOrder")
select p;
IEnumerable<DataRow> rows = expr.ToArray();
foreach (var row in rows)
{
Console.WriteLine(row.Field<string>("ProductName"));
}

var expr = from p in ds.Tables["Product"].AsEnumerable()
orderby p.Field<int>("SortOrder"), p.Field<string>("ProductName") descending
select p;

var query = from p in ds.Tables["Product"].AsEnumerable()
from c in ds.Tables["Category"].AsEnumerable()
where p.Field<int>("CategoryID") == c.Field<int>("CategoryID")
&& p.Field<decimal>("UnitPrice") > 10m
select new
{
ProductID = p.Field<int>("ProductID"),
ProductName = p.Field<string>("ProductName"),
CategoryName = c.Field<string>("CategoryName")
};5. DataTable分组var query = from p in ds.Tables["Product"].AsEnumerable()
group p by p.Field<int>("CategoryID") into g
select new
{
CategoryID = g.Key,
Products = g
};foreach (var item in query)
{
Console.WriteLine(item.CategoryID);
foreach (var p in item.Products)
{
Console.WriteLine(p.Field<string>("ProductName"));
}
}

var expr = from p in ds.Tables["Product"].AsEnumerable()
group p by p.Field<int>("CategoryID") into g
select new
{
CategoryID = g.Key,
ProductsCount = g.Count()
};