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

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日久生厌
日久生厌 2021-01-04 22:22

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

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  •  醉梦人生
    2021-01-04 22:45

    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> idLambda = () => id;
    Expression searchExpr = Expression.Equal(prop, idLambda.Body);
    
    Expression> myLambda =
        Expression.Lambda>(searchExpr, param);
    

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