Question

My function get QueryString from some Web page as a string.
I need to parce it, to check, what strategy i must use.

Now my code looks ugly (i think so):

public QueryStringParser(string QueryString)
        {
            if (string.IsNullOrEmpty(QueryString))
            {
                this._mode = Mode.First;
            }
            else if (QueryString.Contains(_FristFieldName) && !QueryString.Contains(_SecondFieldName))
            {
                this._mode = Mode.Second;
            }
            else if (!QueryString.Contains(_FristFieldName) && QueryString.Contains(_SecondFieldName))
            {
                this._mode = Mode.Third;
            }
            else
            {
                throw new ArgumentException("QueryString has wrong format");
            }
        }

There must’n’t be both FieldNames in one QueryString.

How to change this code to be mo readable.

Answer 1

You could put the determination of the Mode into a separate method and return the Mode value; that way you can eliminate the if-else statements

public QueryStringParser(string QueryString)
{
    this._mode = DetermineMode(QueryString);
}

private Mode DetermineMode(string QueryString)
{
    // Input is NULL STRING
    if (string.IsNullOrEmpty(QueryString))
        return Mode.First;

    bool hasFirst = QueryString.Contains(_FristFieldName);
    bool hasSecond = !QueryString.Contains(_SecondFieldName);

    // Query using FirstName
    if (hasFirst && !hasSecond)
        return Mode.Second;

    //Query using SecondName
    if (!hasFirst && hasSecond)
        return Mode.Third;

    //Insufficient info to Query data
    throw new ArgumentException("QueryString has wrong format");
}

[EDIT] Removed the double checking on the existance of field names and use variables instead.