Cleaner way to do a null check in C#? [duplicate]

Answer 1

I have an extension that could be useful for this; ValueOrDefault(). It accepts a lambda statement and evaluates it, returning either the evaluated value or a default value if any expected exceptions (NRE or IOE) are thrown.

    /// <summary>
    /// Provides a null-safe member accessor that will return either the result of the lambda or the specified default value.
    /// </summary>
    /// <typeparam name="TIn">The type of the in.</typeparam>
    /// <typeparam name="TOut">The type of the out.</typeparam>
    /// <param name="input">The input.</param>
    /// <param name="projection">A lambda specifying the value to produce.</param>
    /// <param name="defaultValue">The default value to use if the projection or any parent is null.</param>
    /// <returns>the result of the lambda, or the specified default value if any reference in the lambda is null.</returns>
    public static TOut ValueOrDefault<TIn, TOut>(this TIn input, Func<TIn, TOut> projection, TOut defaultValue)
    {
        try
        {
            var result = projection(input);
            if (result == null) result = defaultValue;
            return result;
        }
        catch (NullReferenceException) //most reference types throw this on a null instance
        {
            return defaultValue;
        }
        catch (InvalidOperationException) //Nullable<T> throws this when accessing Value
        {
            return defaultValue;
        }
    }

    /// <summary>
    /// Provides a null-safe member accessor that will return either the result of the lambda or the default value for the type.
    /// </summary>
    /// <typeparam name="TIn">The type of the in.</typeparam>
    /// <typeparam name="TOut">The type of the out.</typeparam>
    /// <param name="input">The input.</param>
    /// <param name="projection">A lambda specifying the value to produce.</param>
    /// <returns>the result of the lambda, or default(TOut) if any reference in the lambda is null.</returns>
    public static TOut ValueOrDefault<TIn, TOut>(this TIn input, Func<TIn, TOut> projection)
    {
        return input.ValueOrDefault(projection, default(TOut));
    }

The overload not taking a specific default value will return null for any reference type. This should work in your scenario:

class test
{
    private test()
    {
        var person = new Person();
        if (person.ValueOrDefault(p=>p.contact.address.city) != null)
        {
            //the above will return null without exception if any member in the chain is null
        }
    }
}