Use EnsureProperty/EnsureProperties to ensure a property is loaded.

// Implementation taken from PnP Core as example
var dirty = false;
foreach (Expression<Func<T, object>> expression in propertySelector)
{
    if (expression.Body.NodeType == ExpressionType.Call && expression.Body is MethodCallExpression)
    {
        var body = (MethodCallExpression) expression.Body;
        if (body.Method.IsGenericMethod &&
            body.Method.DeclaringType == typeof (ClientObjectQueryableExtension) &&
            (body.Method.Name == "Include" || body.Method.Name == "IncludeWithDefaultProperties"))
        {
            if (body.Arguments.Count != 2)
            {
                throw new Exception("Invalid arguments number");
            }

            clientObject.Context.Load(clientObject, expression);
            dirty = true;
        }
        else
        {
            throw new Exception("Only 'Include' and 'IncludeWithDefaultProperties' methods are supported.");
        }
    }
    else if (!clientObject.IsPropertyAvailable(expression) && !clientObject.IsObjectPropertyInstantiated(expression))
    {
        clientObject.Context.Load(clientObject, expression);
        dirty = true;
    }
    else if (clientObject.IsObjectPropertyInstantiated(expression))
    {
        dirty  = dirty || EnsureCollectionLoaded(clientObject, expression);
    }
}

if (dirty)
{
    clientObject.Context.ExecuteQueryRetry();
}

web.EnsureProperty(w => w.ServerRelativeUrl);