the lambda in your example has "closed over" the
testvalue variable, meaning the compiler has captured it as a field of the same name in an automatically generated class called
consoleapplication1.program+<>c__displayclass1>. you can use normal reflection to get the current value of that field by casting the right hand-side of the binary expression into a memberexpression.
var testvalue = "hello"; var expr = (expression<func<string, bool>>) (x => x == testvalue); var rhs = (memberexpression) ((binaryexpression) expr.body).right; var obj = ((constantexpression) rhs.expression).value; var field = (fieldinfo) rhs.member; var value = field.getvalue(obj); debug.assert(equals(value, "hello")); testvalue = "changed"; value = field.getvalue(obj); debug.assert(equals(value, "changed"));
alternatively you can change your variable into a constant.
const string testvalue = "hello"; var expr = (expression<func<string, bool>>) (x => x == testvalue); var value = ((constantexpression) ((binaryexpression) expr.body).right).value; debug.assert(equals(value, "hello"));
instead of doing this by yourself, have a look at
partialevaluator from matt warren. it replaces all references to constants with the constants themselves.
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