Sequence Contains No Elements

Why is this error, 'Sequence contains no elements', happening?

Check again. Use debugger if must. My guess is that for some item in userResponseDetails this query finds no elements:

.Where(y => y.ResponseId.Equals(item.ResponseId))

so you can't call

.First()

on it. Maybe try

.FirstOrDefault()

if it solves the issue.

Do NOT return NULL value! This is purely so that you can see and diagnose where problem is. Handle these cases properly.

Sequence Contains No Elements Error In C#

You should be checking for a null object:

foreach (AI info in ro.AI) 
{ 
    var addressInfo = info.AddressInfo.FirstOrDefault();

    if(addressInfo != null)
    {
        string address = addressInfo["Address1"]; 
        string address2 = addressInfo["Address2"]; 
        string city = addressInfo["City"];
        string state = addressInfo["State"];
        string zip = addressInfo["Zip"];

        Console.ReadLine();
    }
} 

WEB API Sequence contains no elements

The First() extension method will throw an exception when the source sequence is empty. In this case, it looks like your LINQ expression with that where clause is not returning a valid collection, hence you are getting this error.

You should use FirstOrDefault() and check whether it is null or not before proceeding.

var result = medEntitites.tj_xhqd.Where(m => m.zdjh == msn)
                                             .OrderByDescending(o => o.sjsj)
                                             .Select(s => s.sjsj)
                                             .FirstOrDefault();
if(result==null)
{
  return Request.CreateErrorResponse(HttpStatusCode.NotFound, ex);
}

FirstOrDefault() method returns the first element of a sequence that satisfies the condition or a default value if no such element is found. You will get null if there are no records matching your condition.

Sequence contains no elements in c#

Hi for this question I have used regex to get the string . then I used the same method I posted in the question .

Sequence contains no elements in linq?

you have to use ConcurrentDictionary if you are working with Parallel.

normal dictionaries aren't threadsafe.

Sequence contains no elements', happening?

If First() results in

Sequence contains no elements

That means the condition in the lambda expression resulted in no hits. Because First requires you to have atleast one match.

If FirstOrDefault().Property results in

Object reference not set to an instance of an object

It means that the lambda expression resulted in no hits, and it returns a default value of the return type. In the case of a reference object it will be null. You then tried to access a property of null which causes the exception.

Simply put. Your problem is that your comparison is returning no hits.

You need to insert a fail safe for this to not crash

Something like:

public string GetOfficeNamebyNumber(string officeNumber)
{
    var result = db.Office.FirstOrDefault(g => g.OfficeNumber == officeNumber);

    if(result == null)
        return string.Empty;

    return result.OfficeName;
}

This can also be shortend to

public string GetOfficeNamebyNumber(string officeNumber)
{
    var result = db.Office.FirstOrDefault(g => g.OfficeNumber == officeNumber);

    return result?.OfficeName ?? string.Empty;
}

Or even

public string GetOfficeNamebyNumber(string officeNumber)
{
    return db.Office.FirstOrDefault(g => g.OfficeNumber == officeNumber)?.OfficeName ?? string.Empty;
}

I hope this step by step explanation gives you the information you need to solve the problem.

Sequence contains no elements server side

Check in your code to make sure FirstOrDefault() or SingleOrDefault() is used instead of using any of these: First() or Single().

When you get theLINQ Error "Sequence contains no elements", this is
usually because you are using the First() or Single() command rather
than FirstOrDefault() and SingleOrDefault().

Sequence contains no elements?

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