如何仅从一列获取一行数据 [英] How to get one row data from one column only

问题描述

当我写作



foreach（dt.Rows中的DataRow行）

{

html .Append（）;

foreach（dt.Columns中的DataColumn列）

{

html.Append（）;

}

html.Append（

）; html.Append（row [column.ColumnName]）; html.Append（

）; string file = row [EmailID]。ToString（）; i我收到所有用户的所有电子邮件ID。我想只有一个用户的电子邮件ID。我怎么能得到这个？

when i am writing

foreach (DataRow row in dt.Rows)
{
html.Append("");
foreach (DataColumn column in dt.Columns)
{
html.Append("");
}
html.Append("

"); html.Append(row[column.ColumnName]); html.Append("

"); string file = row["EmailID"].ToString(); i am getting all email ids of all users. I want email id of only one user. How can I get this??

推荐答案

有几种方法，但我' d首先检索您感兴趣的用户的信息。而不是SELECT查询是一般的：

There are a couple of ways, but I'd start by retrieving only the info the one user you are interested in. Instead of your SELECT query being general:

SELECT * FROM MyTable

添加WHERE子句：

Add a WHERE clause:

SELECT * FROM MyTable WHERE userID = 12345

这样，你没有得到你不打算使用的信息（效率更高）而且不必根本使用循环（甚至是DataTable和DataAdapter - 如果你想要的只是电子邮件ID，那么你可以指定列名，并使用ExecuteScalar返回单个值。）

That way, you aren't getting info you don't intend to use (which is a lot more efficient) and don't have to use a loop at all (or even a DataTable and DataAdapter - if all you want is the email id, then you can specify the column name, and use ExecuteScalar to return a single value).

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