C# 使用 where 子句过滤数据表行
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Filtering a datatable row using a where clause
提问by Csharp
I have a DataTable that I am pulling from a DataSet. From the DataTable, I want to use the Where clause to return a particular row. I looked at "How can I select a row from a datatable using two variable values?" but I get an error
我有一个从数据集中提取的数据表。从数据表中，我想使用 Where 子句返回特定行。我查看了“如何使用两个变量值从数据表中选择一行？”但出现错误
"Cannot implicitly convert type 'System.Data.DataRow[]' to 'System.Data.DataRow'"
“无法将类型 'System.Data.DataRow[]' 隐式转换为 'System.Data.DataRow'”
I searched google, but could not find a solution.
我搜索了谷歌，但找不到解决方案。
My code is:
我的代码是：
mySqlDataAdapter.Fill(myDataSet);
DataTable dtTable = myDataSet.Tables[0];
DataRow dr = dtTable.Select("VendorID = " + Session["VendorId"].ToString());
How can I resolve this?
我该如何解决这个问题？
采纳答案by Steve
The Selectmethod of a DataTable returns an array of DataRow even if your query selects only one row
即使您的查询仅选择一行，DataTable的Select方法也会返回一个 DataRow 数组
DataRow[] dr = dtTable.Select("VendorID = " + Session["VendorId"].ToString());
Then, if you really expects just one row, you could easily grab the expected row checking for the length of the array. In this case it is my opinion that no fancy Enumerable extension methods are really needed
然后，如果您真的只需要一行，您可以轻松获取预期的行，检查数组的长度。在这种情况下，我认为真的不需要花哨的 Enumerable 扩展方法
if(dr.Length > 0)
{
string avalue = dr[0]["AColumnName"].ToString();
...
}
回答by Jonesopolis
Select() is returning an array of rows, and you're assigning it to a single row.
Select() 返回一个行数组，您将其分配给一行。
You can do :
你可以做 ：
DataRow dr = dtTable.Select("VendorID = " + Session["VendorId"].ToString()).First();
or
或者
var dr = dtTable.Select("VendorID = " + Session["VendorId"].ToString());
which will give you an array of rows.
这会给你一个行数组。
回答by Oscar
Asuming there is only one unique result
假设只有一个唯一结果
DataTable dtTable = myDataSet.Tables[0];
DataRow[] drs = dtTable.Select("VendorID = " + Session["VendorId"].ToString());
if(drs.Length > 0)
DataRow dr = drs[0];
回答by Jason P
DataTable.Select()returns an array of DataRow.
DataTable.Select()返回一个数组DataRow。
DataRow[] dr = dtTable.Select("VendorID = " + Session["VendorId"].ToString());
If you only want the first record,
如果你只想要第一条记录，
DataRow[] dr = dtTable.Select("VendorID = " + Session["VendorId"].ToString()).FirstOrDefault();
回答by Forte L.
Use the method First():
使用方法First()：
DataRow dr = dtTable.Select("VendorID = " + Session["VendorId"].ToString()).First();
回答by Harkonnen
The Select() method returns an IEnumerable collection with one DataRow inside, in your case. You must extract the DataRow from that collection with FirstOrDefault() instead.
在您的情况下， Select() 方法返回一个 IEnumerable 集合，其中包含一个 DataRow 。您必须改为使用 FirstOrDefault() 从该集合中提取 DataRow。
