CODEWITHSUNDEEP
c#-3.0lambda
csano
csano

Reputation: 13686

Detecting that a MemberExpression has a value

How do I detect if a MemberExpression has a value that needs to be compiled/evaluated?

I have two separate member expression outputs, the first which has a value, and the second which doesn't. What is the best way to differentiate between the two?

exp
**{value(Microsoft.Connect.Api.Client.Tests.SearchQueryUnitTests+<>c__DisplayClass6).handle}**
    [System.Linq.Expressions.MemberExpression]: **{value(Microsoft.Connect.Api.Client.Tests.SearchQueryUnitTests+<>c__DisplayClass6).handle}**
    NodeType: MemberAccess
    Type: {Name = "String" FullName = "System.String"}

vs

exp
{x.CreatedBy}
    [System.Linq.Expressions.MemberExpression]: {x.CreatedBy}
    NodeType: MemberAccess
    Type: {Name = "String" FullName = "System.String"}

Upvotes: 2

Views: 418

Answers (1)

casperOne
casperOne

Reputation: 74540

I see two different answers to this.

Are you trying to create a conditional with expressions and then do something with the result? If that is the case, you will create a BinaryExpression of type Equals (call the static Equals method on the Expression class) passing in the MemberExpression as left, and then passing another expression representing a non-value (null if a reference type, or a new instance of the struct if a value type).

If you are actually trying to evaluate the expression at that point, then I would create a lambda which actually returns the expression, compile it, and then check against a non-value in your code.

Upvotes: 1

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