# “StringPlusNull”  (Solution)

## Answer

```
False
```

## Explanation

A text fragment from [C# Language Specification](http://www.microsoft.com/downloads/en/details.aspx?FamilyID=DFBF523C-F98C-4804-AFBD-459E846B268E), the “7.8.4 Addition operator” section:

“String concatenation:

```csharp
string operator +(string x, string y);
string operator +(string x, object y);
string operator +(object x, string y);
```

These overloads of the binary + operator perform string concatenation. **If an operand of string concatenation is null, an empty string is substituted**. Otherwise, any non-string argument is converted to its string representation by invoking the virtual ToString method inherited from type object. If ToString returns null, an empty string is substituted.”

Thus:

```csharp
((string)null + null + null) == ("" + null + null) ==
  (("" + null) + null) == (("" + "") + null) == ("" + null) ==
  ("" + "") == ""
"" != null
```

## Links

* [Microsoft Reference Source](http://referencesource.microsoft.com/#mscorlib/system/string.cs)
* [Mono 3.10.0 Source](https://github.com/mono/mono/blob/mono-3.10.0/mcs/class/corlib/System/String.cs)

[Problem](https://andreyakinshin.gitbook.io/problembookdotnet/en/strings/stringplusnull-p)