C#•2y ago

❔ ✅ Get name of assigned property in an Expression

I am (partially for fun) writing the following method:

void BulkMerge<T, TConstraint>(
  IEnumerable<T> entities, 
  Expression<Func<T, TConstraint>> constraintSelector
) {
  //
}

void BulkMerge<T, TConstraint>(
  IEnumerable<T> entities, 
  Expression<Func<T, TConstraint>> constraintSelector
) {
  //
}

Here is how I intend to call it:

BulkMerge(accounts, (a) => new { AccountID = a.Id });

BulkMerge(accounts, (a) => new { AccountID = a.Id });

I'd like to parse the Expression argument above such that I have

var maps = constraintSelector.ExtractMaps();

var maps = constraintSelector.ExtractMaps();

Where ExtractMaps is an extension method that returns this structure (denoted in JSON for clarity)

[ { "Source": "Id", "Destination", "AccountID" } ]

[ { "Source": "Id", "Destination", "AccountID" } ]

Is this possible in C#?

5 Replies

Anton•2y ago

your constraint selector is an expression tree. go through the individual nodes and figure out what you got there should be a visitor base class for that, or just go through them manually you are expecting a certain structure after all

cdbusOP•2y ago

🦥 fine... Thank you

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

cdbusOP•2y ago

@AntonC just following up, got this working perfectly 👍 Wrote an ExpressionVisitor subclass, and the rest is history

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ ✅ Get name of assigned property in an Expression