Creates a lookup object from a sequence.
// lookup.A[0] = 'Albert'
// lookup.B[0] = 'Bill'
// lookup.B[1] = 'Barney'
// lookup.K[0] = 'Konrad'
// lookup.M[0] = 'Marcel'
var lookup = Enumerable.create('Bill', 'Marcel', 'Barney', 'Albert', 'Konrad')
.toLookup('x => x[0]');
With equality comparer
// lookup.A[0] = 'Albert'
// lookup.b[0] = 'bill'
// lookup.B[0] = 'Barney'
// lookup.K[0] = 'Konrad'
// lookup.M[0] = 'Marcel'
var lookup = Enumerable.create('bill', 'Marcel', 'Barney', 'Albert', 'Konrad')
.toLookup('x => x[0]',
'x, y => x === y');