循环遍历列表并将前一行与当前行进行比较。 我有一个帐号列表，其中大部分是重复的

Question

My result two is a list of account numbers and dates that I have added from another list by using LINQ to sort. The list of result two contains many duplicate account numbers but I would like to filter the list to remove duplicates but not just selecting the first instance.

I am looking to select the account number that has the oldest date. I'm getting some output from the stream reader but its not behaving as expected. I am still getting every line and no removals.

I'm trying to compare if the account number matches the account number from the previous line and the current date is older to remove the instance of the account number with the newer date.

Any ideas?

    foreach (var valueTwo in resultTwo)
    {
        var valueString = valueTwo.Name.ToString();
        var currentAccount = valueString.Substring(0, valueString.IndexOf('\t'));
        var currentDateTwo = (valueString.Substring((valueString.IndexOf('\t') + 1), 10).Replace("/", ""));
        int currentDate = Convert.ToInt32(currentDateTwo);
        var prevAccount = "";
        int prevDate = 0;

        if (currentAccount != prevAccount)
        {
            forecastTestList.Add(currentAccount + '\t' + currentDate);
        }

        if (currentAccount == prevAccount)
        {
            if (currentDate > prevDate)
            {
                forecastTestList.Remove(prevAccount + '\t' + prevDate);
                forecastTestList.Add(currentAccount + '\t' + currentDate);
            }
        }
        prevAccount = currentAccount;
        prevDate = currentDate;

        //srcheckForecast.WriteLine(valueTwo.Name);
    }

    foreach (var valueThree in forecastTestList)
    {
        srcheckForecast.WriteLine(valueThree);
    }
}

Answer 1

An alternative approach would be to use Dictionary data structure to store the maximum day for each account:

var dictionary = new Dictionary<string, int>();

foreach (var valueTwo in resultTwo)
{
    var valueString = valueTwo.Name.ToString();
    var currentAccount = valueString.Substring(0, valueString.IndexOf('\t'));
    var currentDateTwo = (valueString.Substring((valueString.IndexOf('\t') + 1), 10).Replace("/", ""));
    int currentDate = Convert.ToInt32(currentDateTwo);

    if (!dictionary.TryGetValue(currentAccount, out int value) || currentDate > value)
    {
        dictionary[currentAccount] = currentDate;
    }   
}

// transorm dictionary to List<string> of your form
var forecastTestList = dictionary.Select(x => $"{x.Key + '\t' + x.Value}").ToList();