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copied!<p>Give the code below a run. I wanted to test your assumption that e => e.Location == location is compiling into something that can be constructed with Expression.Equal, Expression.Property, and Expression.Constant.</p> <pre><code> class Program { static void Main(string[] args) { var location = new Location(); Expression<Func<Employee, bool>> expression = e => e.Location == location; var untypedBody = expression.Body; //The untyped body is a BinaryExpression Debug.Assert( typeof(BinaryExpression).IsAssignableFrom(untypedBody.GetType()), "Not Expression.Equal"); var body = (BinaryExpression)untypedBody; var untypedLeft = body.Left; var untypedRight = body.Right; //The untyped left expression is a MemberExpression Debug.Assert( typeof(MemberExpression).IsAssignableFrom(untypedLeft.GetType()), "Not Expression.Property"); ////The untyped right expression is a ConstantExpression //Debug.Assert( // typeof(ConstantExpression).IsAssignableFrom(untypedRight.GetType()), // "Not Expression.Constant"); //The untyped right expression is a MemberExpression? Debug.Assert( typeof(MemberExpression).IsAssignableFrom(untypedRight.GetType()))); } } public class Employee { public Location Location { get; set; } } public class Location { } </code></pre> <p>It seems like it isn't, and its because the right expression isn't a Constant. To see this, uncomment the commented out code.</p> <p>What I don't understand is why the right expression is a MemberExpression. Perhaps someone who knows the linq expression compiler can shed more light onto this then I can.</p> <p>Edit: This may have to do with closure in lambdas - a class is created behind the scenes which contains the closed over variables. The location might then be a member of that class. I'm not sure about this, but it's what I suspect.</p> <p><a href="https://stackoverflow.com/questions/3991621/can-i-capture-a-local-variable-into-a-linq-expression-as-a-constant-rather-than">This post</a> may shed additional light on the situation.</p>

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