&#101xecuteScalar 方法
2024-07-21 02:22:28
供稿：网友
使用 executescalar 方法从数据库中检索单个值（例如一个聚合值）。与使用 executereader 方法，然后使用 sqldatareader 返回的数据执行生成单个值所需的操作相比，此操作需要的代码较少。
典型的 executescalar 查询可以采用类似于下面的 c# 示例的格式：
commandtext = "select count(*) as numberofregions from region";
int count = (int) executescalar();
例子：
<%@ import namespace="system.data" %>
<%@ import namespace="system.data.sqlclient" %>
<script language="vb" runat="server">
sub page_load(byval sender as system.object, byval e as system.eventargs)
if not ispostback then
dim dtstartdate as datetime = datetime.now.adddays(-7)
dim dtenddate as datetime = datetime.now.adddays(-1)
startdate.text = dtstartdate.toshortdatestring
enddate.text = dtenddate.toshortdatestring
literal1.text = geteditionnumber()
end if
end sub
function geteditionnumber()
dim conn as sqlconnection = new sqlconnection(configurationsettings.appsettings("dsn"))
dim cmd as sqlcommand = new sqlcommand("select max(id) from table", conn)
conn.open()
dim id as string = cmd.executescalar
conn.close()
return id
end function
</script>
<html>
<head></head>
<body>
<form runat="server">
<asp:literal id="literal1" runat="server" /><br>
<asp:textbox id="startdate" runat="server"></asp:textbox><br>
<asp:textbox id="enddate" runat="server"></asp:textbox>
</form>
</body>
</html>web.config used in example<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appsettings>
<add key="dsn" value="server=localhost;uid=sa;pwd=;database=pubs"/>
</appsettings>
</configuration>
