private static Func <TIn, TOut> CompileFromFingerprint(Expression <Func <TIn, TOut> > expr)
            {
                List <object> capturedConstants;
                ExpressionFingerprintChain fingerprint =
                    FingerprintingExpressionVisitor.GetFingerprintChain(
                        expr,
                        out capturedConstants
                        );

                if (fingerprint != null)
                {
                    var del = _fingerprintedCache.GetOrAdd(
                        fingerprint,
                        _ =>
                    {
                        // Fingerprinting succeeded, but there was a cache miss. Rewrite the expression
                        // and add the rewritten expression to the cache.

                        var hoistedExpr = HoistingExpressionVisitor <TIn, TOut> .Hoist(expr);
                        return(hoistedExpr.Compile());
                    }
                        );
                    return(model => del(model, capturedConstants));
                }

                // couldn't be fingerprinted
                return(null);
            }
            private static Func <TIn, TOut> CompileFromFingerprint(Expression <Func <TIn, TOut> > expr)
            {
                List <object> capturedConstants;
                ExpressionFingerprintChain fingerprintChain = FingerprintingExpressionVisitor.GetFingerprintChain(expr, out capturedConstants);

                if (fingerprintChain != null)
                {
                    Hoisted <TIn, TOut> del = CachedExpressionCompiler.Compiler <TIn, TOut> ._fingerprintedCache.GetOrAdd(fingerprintChain, delegate(ExpressionFingerprintChain _)
                    {
                        Expression <Hoisted <TIn, TOut> > expression = HoistingExpressionVisitor <TIn, TOut> .Hoist(expr);
                        return(expression.Compile());
                    });

                    return((TIn model) => del(model, capturedConstants));
                }
                return(null);
            }