使用LINQ to sql检查记录是否已存在 [英] Check if record already exist using LINQ to sql

问题描述

HI：

我正在使用LINQ to sql with c＃

我在网页上输入一个文本框后输入一个值

如果myTable中存在此值，我需要验证

HI:
I'm using LINQ to sql with c#
I have a text box on a web page , after entering a value to that box
I need to validate whither if this value exist in myTable or not

Var xmyTable = (from ymyTable in objDataContext.myTables
                              Select new 
                             {
                               ymyTable.myCode
                              ymyTable.myNmae
                             }

请帮助

please help

推荐答案

首先将文本框的值存储在一个字符串中，并从匹配该字符串的数据库中检索值。这里我将名称作为文本框的值。

1st of all store the textbox's value in a string and retrieve value from database matching that sting. here i am taking name as the textbox's value.

 string s = textBox1.text;
var xmyTable = (from ymyTable in objDataContext.myTables where ymyTable.myName == s
                  Select new {ymyTable.myCode,ymyTable.myNmae}).FirstorDefault();
if(xmyTable.Count>0)
{
//your logic for record found.
} 
else
{
//your logic for record not found
}  

您好，您可以使用lambda expresion写这样的查询



http://stackoverflow.com/questions/6330682/select-count-in-linq-to-sql-c-sharp [ ^ ]

Hi you can write query like this using lambda expresion

http://stackoverflow.com/questions/6330682/select-count-in-linq-to-sql-c-sharp[^]

if(objDataContext.myTables.Count((a)=>a.name=="some name")==0)
{
//Record not present
}
else
{
//Record is present
}

(a)=>a.name=="some name"

适用于哪种情况

hope对你有帮助。

is for where condition
hope it is helpful to you.

var v=objDataContext.myTables.FirstOrDefault(p=>p.myCode=text box value);
if (!v=Null)
{
}

希望有所帮助

Hope it helps

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