Question

there is a method that receives an int parameter and returns a string by checking parameter through a set of if…else statements :

if(param == 1)
{
    return "1";
}
else if(param ==20)
{
    return "20";
}
else
{
    if(param <= 10)
    {
        return "below 10";
    }
    else if(param <= 30 )
    {
        return "below 30";
    }
    ...
}

I wonder if it is possible to put these “>= , <=” conditions in a dictionary

Answer 1

You can use Dictionary<Func<int, bool>, string>:

    private string Do(int input)
    {
        var dic = new Dictionary<Func<int, bool>, string>
            {
                {param => param == 1, "1"},
                {param => param == 20, "20"},
                {param => param <= 10, "below 10"},
                {param => param <= 30, "blow 30"}
            };

        return dic.First(pair => pair.Key(input)).Value;  
    }

Edit:

Comment from @Maarten is correct, Dictionary does not ensure the order of item, List of KeyValuePair should be the best this case:

    private string Do(int input)
    {
        var pairs = new List<KeyValuePair<Func<int, bool>, string>>
            {
                {param => param == 1, "1"},
                {param => param == 20, "20"},
                {param => param <= 10, "below 10"},
                {param => param <= 30, "blow 30"}
            };

        var pair = pairs.FirstOrDefault(pair => pair.Key(input));
        if (pair == null) return string.Empty; // return whatever you want

        return pair.Value;
    }