Resolving a parameter name at runtime [duplicate]

Answer 1

You might want:

1)

public static void ThrowIfNull(Expression> expr)
{
    if (expr == null || expr.Compile()() != null) //the compile part is slow
        return;

    throw new ArgumentNullException(((MemberExpression)expr.Body).Member.Name);
}

or

2)

public static void ThrowIfNull(Expression> expr)
{
    if (expr == null)
        return;

    var param = (MemberExpression)expr.Body;
    if (((FieldInfo)param.Member).GetValue(((ConstantExpression)param.Expression).Value) == null)
        throw new ArgumentNullException(param.Member.Name);
}

And call it:

Class.ThrowIfNull(() => resource);

But that's not what you would want probably. Its also a lot slower 1) is abt 1000 times slower than 2). May be:

3)

public static void ThrowIfNull(this T item) where T : class
{
    if (item == null)
        return;

    var param = typeof(T).GetProperties()[0];
    if (param.GetValue(item, null) == null)
        throw new ArgumentNullException(param.Name);
}

And call it:

new { resource }.ThrowIfNull();

Cleaner, much faster than above 2! :)

You can also extend these methods for properties of objects. For eg.,

new { myClass.MyProperty1 }.ThrowIfNull();

You can cache property values to improve performance further as property names don't change during runtime. See related question Finding the variable name passed to a function