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    <p>[updated for clarity]</p> <p>First; cast the <code>Expression</code> to a <code>MemberExpression</code>.</p> <p>A <code>MemberExpression</code> has two things of interest:</p> <ul> <li>.Member - the <code>PropertyInfo</code> / <code>FieldInfo</code> to the member</li> <li>.Expression - the expression to evaluate to get the "obj" for the .Member</li> </ul> <p>i.e. if you can evaluate the <code>.Expression</code> to "obj", and the <code>.Member</code> is a <code>FieldInfo</code>, then you can get the actual value via <code>.GetValue(obj)</code> on the <code>FieldInfo</code> (and <code>PropertyInfo</code> is very similar).</p> <p>The problem is that evaluating the <code>.Expression</code> is very tricky ;-p</p> <p>Obviously you get lucky if it turns out to be a <code>ConstantExpression</code> - but in most cases it isn't; it could be a <code>ParameterExpression</code> (in which case you'll need to know the actual parameter value that you want to evaluate), or any other combination of <code>Expression</code>s.</p> <p>In many cases, a simple (perhaps lazy) option is to use <code>.Compile()</code> to get the .NET framework to do the heavy lifting; you can then evaluate the lambda as a typed delegate (passing in any parameters that the lambda requires). This isn't always an option, however.</p> <p>To show how complex this is; consider this trivial example (where I've hard-coded at every step, rather than testing etc):</p> <pre><code>using System; using System.Linq.Expressions; using System.Reflection; class Foo { public string Bar { get; set; } } static class Program { static void Main() { Foo foo = new Foo {Bar = "abc"}; Expression&lt;Func&lt;string&gt;&gt; func = () =&gt; foo.Bar; MemberExpression outerMember = (MemberExpression)func.Body; PropertyInfo outerProp = (PropertyInfo) outerMember.Member; MemberExpression innerMember = (MemberExpression)outerMember.Expression; FieldInfo innerField = (FieldInfo)innerMember.Member; ConstantExpression ce = (ConstantExpression) innerMember.Expression; object innerObj = ce.Value; object outerObj = innerField.GetValue(innerObj); string value = (string) outerProp.GetValue(outerObj, null); } } </code></pre>
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    1. POGiven a type ExpressionType.MemberAccess, how do i get the field value?
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    1. USMarc Gravell
    1. USMarc Gravell
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    1. POGiven a type ExpressionType.MemberAccess, how do i get the field value?
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    1. COThank you so much Marc. THe value of .Expression property is ... something more interesting: {value(ASP.usercontrols_mycontro_ascx).controlname}
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      1. USKeith Fitzgerald
    2. COi'm doing a lot with generics and reflection so retrieving the value via propertyinfo/fieldinfo isn't working because i'm not sure where to pull the referencing object from ... can i pull that from memberexpression or methodinfo?
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    3. COIt will work... but the problem is you need to evaluate the .Expression as a value to feed in as the "obj" for FieldInfo/PropertyInfo. Can you not just use .Compile() and execute the lambda as a delegate? A lot easier than parsing...
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