Is there any way to indicate to ReSharper that a null reference won&#39;t occur because of Design-by-Contract Requires checking?  For example, the following code will raise the warning (`Possible &#39;null&#39; assignment to entity marked with &#39;NotNull&#39; attribute`) in ReSharper on lines 7 and 8:


    private Dictionary&lt;string, string&gt; _Lookup = new Dictionary&lt;string, string&gt;();

    public void Foo(string s)
    {
        Contract.Requires(!String.IsNullOrEmpty(s));
        
        if (_Lookup.ContainsKey(s))
            _Lookup.Remove(s);
    }

What is really odd is that if you remove the `Contract.Requires(...)` line, the ReSharper message goes away. 

**Update**

I found the solution through ExternalAnnotations which was also mentioned by Mike below.  Here&#39;s an example of how to do it for a function in Microsoft.Contracts:

* Create a directory called `Microsoft.Contracts` under the `ExternalAnnotations` ReSharper directory.
* Next, Create a file called `Microsoft.Contracts.xml` and populate like so:

&lt;xml&gt;

    &lt;assembly name=&quot;Microsoft.Contracts&quot;&gt;
        &lt;member name=&quot;M:System.Diagnostics.Contracts.Contract.Requires(System.Boolean)&quot;&gt;
            &lt;attribute ctor=&quot;M:JetBrains.Annotations.AssertionMethodAttribute.#ctor&quot;/&gt;
            &lt;parameter name=&quot;condition&quot;&gt;
                &lt;attribute ctor=&quot;M:JetBrains.Annotations.AssertionConditionAttribute.#ctor(JetBrains.Annotations.AssertionConditionType)&quot;&gt;
                    &lt;argument&gt;0&lt;/argument&gt;
                &lt;/attribute&gt;
            &lt;/parameter&gt;
        &lt;/member&gt;
    &lt;/assembly&gt;
&lt;/xml&gt;

* Restart Visual Studio, and the message goes away!

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ReSharper - Possible Null Assignment when using Microsoft.Contracts