为什么我不能在C＃中比较两个ID

Question

I tried to compare two ids and get some result.it works for other strings.but not for this. I tried like this.

var neededData = mainFaires.Where(c => c.trimacid == passId );

in here passId= OX20160330HAVHAV

and in the mainFaires list, in somewhere it includes this id .but it didn't give the result.I found in here

var x = mainFaires.ElementAt(27261);

this list include the same id .but didn't give result.I can't think why.

Answer 1

ElementAt is find the position.

You should use select to find the records

var x = mainFaires.Select(o => o.trimacid == 27261);

Answer 2

You should use .ToList() .First() or .FirstOrDefault() to actually commit the query and get a result. Your code only defined the query, but didn't actually submit it to the data collection.

If you expect only one item as a result, you're code should look like this:

var neededData = mainFaires.Where(c => c.trimacid == passId ).FirstOrDefault();

If there was no item found, neededData would be NULL or whatever the default value is. You may also check the Documentation here https://msdn.microsoft.com/en-us/library/system.linq.enumerable%28v=vs.100%29.aspx