should RedisValue.HasValue check for valueBlob != IntegerSentinel?

[jamesmanning]

Currently a RedisValue created from an int or long will have valueBlob == IntegerSentinel, and since IntegerSentinel is an empty array, HasValue will be false.

StackExchange.Redis/StackExchange.Redis/StackExchange/Redis/RedisValue.cs

Lines 52 to 72 in 12e6114

	/// <summary>
	/// Indicates whether the value is either null or a zero-length value
	/// </summary>
	public bool IsNullOrEmpty
	{
	get
	{
	return valueBlob == null || (valueBlob.Length == 0 && !(valueBlob == IntegerSentinel));
	}
	}
	/// <summary>
	/// Indicates whether the value is greater than zero-length
	/// </summary>
	public bool HasValue
	{
	get
	{
	return valueBlob != null && valueBlob.Length > 0;
	}
	}

This might be ByDesign, but it seemed strange since it appears RedisValue instances holding an int or long still have a 'value', just stored in the valueInt64 field instead of the valueBlob one.

[NickCraver]

@mgravell did we ever revisit this? Appears to still be an issue in current code:

public bool IsNullOrEmpty => valueBlob == null || (valueBlob.Length == 0 && !(valueBlob == IntegerSentinel));
public bool HasValue => valueBlob?.Length > 0;

A simple test locally:

RedisValue val = 4;
Console.WriteLine(val.IsNullOrEmpty); // false - correct
Console.WriteLine(val.HasValue);      // false - incorrect

IMO, the best fix here is to simply make HasValue:

public bool HasValue => !IsNullOrEmpty;

I've opened up a PR (#840) to resolve this.