C# 使用 LINQ 更新数据表中的两列
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Update two columns in a DataTable using LINQ
提问by Jainendra
I want to update two columns of DataTable in a single line using LINQ query. Currently I am using following two lines to do the same:
我想使用 LINQ 查询在一行中更新 DataTable 的两列。目前我正在使用以下两行来做同样的事情：
oldSP.Select(string.Format("[itemGuid] = '{0}'", itemGuid)).ToList<DataRow>().ForEach(r => r["startdate"] = stDate);
oldSP.Select(string.Format("[itemGuid] = '{0}'", itemGuid)).ToList<DataRow>().ForEach(r => r["enddate"] = enDate);
How can I do this in one line, using one Select?
我怎样才能在一行中做到这一点，使用 one Select？
采纳答案by Sergey Berezovskiy
You can do it in one 'line', just pass appropriate action delegate to ForEach method:
您可以在一行中完成，只需将适当的动作委托传递给 ForEach 方法：
oldSP.Select(string.Format("[itemGuid] = '{0}'", itemGuid))
.ToList<DataRow>()
.ForEach(r => {
r["startdate"] = stDate;
r["enddate"] = enDate;
});
Also you can use LINQ to DataSet (looks more readable to me, than one-liner):
你也可以使用 LINQ to DataSet（对我来说看起来比单行更具可读性）：
var rowsToUpdate =
oldSP.AsEnumerable().Where(r => r.Field<string>("itemGuid") == itemGuid);
foreach(var row in rowsToUpdate)
{
row.SetField("startdate", stDate);
row.SetField("enddate", enDate);
}
回答by Réda Mattar
Try this :
尝试这个 ：
oldSP.Select(string.Format("[itemGuid] = '{0}'", itemGuid)).ToList<DataRow>()
.ForEach(r => { r["startdate"] = stDate; r["enddate"] = enDate; });
回答by gzaxx
Use curly bracers to do two on more operations:
使用花括号在更多操作上做两个：
oldSP.Select(string.Format("[itemGuid] = '{0}'", itemGuid))
.ToList<DataRow>()
.ForEach(r => { r["enddate"] = enDate); r["startdate"] = stDate; });
But for code readability I would use old-fashioned foreachloop.
但是为了代码可读性，我会使用老式foreach循环。
回答by user2959284
I didn't like any of the examples I saw on the web, so here's my example
我不喜欢我在网上看到的任何例子，所以这是我的例子
DataTable dt = new DataTable();
dt.Columns.Add("Year");
dt.Columns.Add("Month");
dt.Columns.Add("Views");
for (int year = 2011; year < 2015; year++)
{
for (int month = 1; month < 13; month++)
{
DataRow newRow = dt.NewRow();
newRow[0] = year;
newRow[1] = month;
newRow[2] = 0;
dt.Rows.Add(newRow);
}
}
dataGridView1.DataSource = dt;
//if using Lambda
//var test = dt.AsEnumerable().Where(x => x.Field<string>("Year") == "2013" && x.Field<string>("Month") == "2").ToList();
var test = (from x in dt.AsEnumerable()
where x.Field<string>("Year") == "2013"
where x.Field<string>("Month") == "2"
select x).ToList();
test[0][0] = "2015";
dt.AcceptChanges();
//if writing to sql use dt.SubmitChanges() instead
//如果写入 sql 使用 dt.SubmitChanges() 代替
