Pangrams implementation using Linq
First a review...

Long extension chains

With lengthy linq chains it's a good idea to break them into multiple lines. Especially here on CR so that we don't have to scroll horizontally.

String interpolation


string answer = pangramCheck ? "pangram" : "not pangram";



We could optimize it as:

var answer = $"{(pangramCheck ? string.Empty : "not ")}pangram";


or you can make it even prettier by encapsulating this logic in an extension:

public static string Negate(this string value, bool negate)
{
    return $"{(negate ? string.Empty : "not ")}{value}";
}


so you then have:

Console.WriteLine("pangram".Negate(isPangram));


Consistency


string text
string answer



Don't you like var for strings because you already use for the other two variables? ;-)

Magic numbers


Enumerable.Range(97, 26)



This would be easier to understand if you used constants:

const string alphabetLength = z - a + 1;
Enumerable.Range('a', alphabetLength)


Not LINQ


.Replace(" ", "").ToLower()



This two kill the linq idea of your question. Consider this instead:

text
    .Select(char.ToLower)
    .Where(char.IsLetter)




Alternative solution

Then an alternative version...

If using a HashSet&lt;char&gt; is still linq-ish enougth then I replaced the Distinct with the Aggregate that uses one and makes it na O(n) solution for the English aphabet:

const int alphabetLength = 'z' - 'a' + 1;
var isPangram =
    text
    .Select(char.ToLower)
    .Where(char.IsLetter)
    .Aggregate(new HashSet&lt;char&gt;(), (acc, next) =&gt; { acc.Add(next); return acc; })
    .Count == alphabetLength;




UPDATE

Well, I forgot that we don't have to scan the entire string. As soon as we have the required chars we can stop. So this improved version should be faster for long texts:

const int alphabetLength = 'z' - 'a' + 1;
var chars = new HashSet&lt;char&gt;();

var testedChars = text
    .Select(char.ToLower)
    .Where(char.IsLetter)
    .TakeWhile(x =&gt; { chars.Add(x); return chars.Count != alphabetLength; })
    .Count();

var isPangram = chars.Count == alphabetLength;