, BitFlipper wrote

public static extension class string

{
    public static string Longest(string s1, string s2)
    {
        if (s1 == null)
            return s2;

        if (s2 == null)
            return s1;

        return s1.Length >= s2.Length ? s1 : s2;
    }
}

...or...

public static extension struct float
{
    public static float[] FromPcm16(Int16[] srcBuffer)
    {
        var dstBuffer = new float[srcBuffer.Length];

        // Convert to float...
       
        return dstBuffer;
    }
}

What's wrong with 

public static class StringHelper

{
    public static string Longest(string s1, string s2)
    {
        if (s1 == null)
            return s2;

        if (s2 == null)
            return s1;

        return s1.Length >= s2.Length ? s1 : s2;
    }
}

...or...

public static struct FloatHelper
{
    public static float[] FromPcm16(Int16[] srcBuffer)
    {
        var dstBuffer = new float[srcBuffer.Length];

        // Convert to float...
       
        return dstBuffer;
    }
}