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);
}
// Returns the fingerprint chain + captured constants list for this expression, or null
// if the expression couldn't be fingerprinted.
public static ExpressionFingerprintChain GetFingerprintChain(
Expression expr,
out List <object> capturedConstants
)
{
FingerprintingExpressionVisitor visitor = new FingerprintingExpressionVisitor();
visitor.Visit(expr);
if (visitor._gaveUp)
{
capturedConstants = null;
return(null);
}
else
{
capturedConstants = visitor._seenConstants;
return(visitor._currentChain);
}
}