LINQ to DataSet的DataTable操作

最新推荐文章于 2022-05-29 15:27:16 发布

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最新推荐文章于 2022-05-29 15:27:16 发布

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原文链接：http://www.cnblogs.com/haofaner/p/5166622.html

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()
           };

转载于:https://www.cnblogs.com/haofaner/p/5166622.html