How to declare a Linq Expression variable in order to have it processed as a dbParameter

Question

I\'m trying to create dynamic queries against Entity framework (or other Linq provider).

Let me explain my problem with some sample code.

If I hardcode an ex

Answer 1

You'll need to create a lambda at compile time to close over the id variable, to which you can then grab the body of an use in the composition of your more complex lambda:

var id = 12345;
ParameterExpression param = Expression.Parameter(typeof(ItemSearch), "s");
Expression prop = Expression.Property(param, "Id");
Expression<Func<int>> idLambda = () => id;
Expression searchExpr = Expression.Equal(prop, idLambda.Body);

Expression<Func<ItemSearch, bool>> myLambda =
    Expression.Lambda<Func<ItemSearch, bool>>(searchExpr, param);