Simple code
I am developer so let’s start with following C# code:
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public static void Main()
{
var sampleList = GetSamples();
if (sampleList.FirstOrDefault().StartsWith("I"))
{
Console.WriteLine("First element starts with I");
}
else
{
Console.WriteLine("First element doesn't start with I");
}
} It compile without any warnings, which is quite cool, But will it work without problems? Of course it depends on `GetSamples` function. But it should, isn't it?
Full implementation
So let’s extend above code to full implementation:
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static readonly Random Random = new Random();
static List<string> GetSamples()
{
if (Random.Next(100) > 2)
{
return new List<string>{"I"};
}
return new List<string>();
}
public static void Main()
{
var sampleList = GetSamples();
if (sampleList.FirstOrDefault().StartsWith("I"))
{
Console.WriteLine("First element starts with I");
}
else
{
Console.WriteLine("First element doesn't start with I");
}
}
Now it starts to look tricky and dangerous. But again you will don’t have any warning in Visual Studio.
Resharper to the rescue
If you use R# you will see following warning: 
Using Alt+Entershortcut generate simple fix:
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var firstOrDefault = sampleList.FirstOrDefault();
if (firstOrDefault != null && firstOrDefault.StartsWith("I"))
{
Console.WriteLine("First element starts with I");
}
else
{
Console.WriteLine("First element doesn't start with I");
}
And we are safe now :)
##… but it doesn’t show everything But imagine that instead of FirstOrDefault() the developer used First(), so the above if will be following:
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if (sampleList.First().StartsWith("I"))
In above case it won’t be any warning even in Resharper :(
Sum up
