[Linq]LINQ to DataSet

針對DataTable的資料，若有加工或篩選的需求，Linq 是目前我選用要熟悉的技術。

 LINQ to DataSet 中的查詢

其中範例中，大致分成兩種，一為查詢運算式語法，二為以方法為基礎的查詢語法
其實對我而言，就是一個有from，另一個沒有~
當我遇到要做Order By時，似乎只有看到有from那種語法有範例。

查詢運算式語法

DataTable products = ds.Tables["Product"];

IEnumerable<datarow> query =
    from product in products.AsEnumerable()
    select product;

Console.WriteLine("Product Names:");
foreach (DataRow p in query)
{
    Console.WriteLine(p.Field<string>("Name"));
}

DataTable products = ds.Tables["Product"];

IEnumerable<datarow> query =
    from product in products.AsEnumerable()
    orderby product.Field<decimal>("ListPrice") descending
    select product;

// Force immediate execution of the query.
IEnumerable<datarow> productsArray = query.ToArray();

Console.WriteLine("Every price from highest to lowest:");
foreach (DataRow prod in productsArray)
{
    Console.WriteLine(prod.Field<decimal>("ListPrice"));
}

以方法為基礎的查詢語法

DataTable products = ds.Tables["Product"];

var query = products.AsEnumerable().
    Select(product => new
    {
        ProductName = product.Field<string>("Name"),
        ProductNumber = product.Field<string>("ProductNumber"),
        Price = product.Field<decimal>("ListPrice")
    });

Console.WriteLine("Product Info:");
foreach (var productInfo in query)
{
    Console.WriteLine("Product name: {0} Product number: {1} List price: ${2} ",
        productInfo.ProductName, productInfo.ProductNumber, productInfo.Price);
}