Question

I have the following file and I am using an iterator block to parse certain re-occuring nodes/parts within the file. I initially used regex to parse the entire file but when certain fields were not present in a node, it would not match. So I am trying to use the yield pattern. The file format is as follows perceeded with the code I am using. All I want from the file are the replicate nodes as an individual part so I can fetch fields within it using a key string and store in collection of objects. I can start parsing where the first replicate occurs but unable to end it where the replicate node ends.

File Format:

X_HEADER
{
    DATA_MANAGEMENT_FIELD_2     NA
    DATA_MANAGEMENT_FIELD_3     NA
    DATA_MANAGEMENT_FIELD_4     NA
    SYSTEM_SOFTWARE_VERSION     NA
}
Y_HEADER
{
    DATA_MANAGEMENT_FIELD_2     NA
    DATA_MANAGEMENT_FIELD_3     NA
    DATA_MANAGEMENT_FIELD_4     NA
    SYSTEM_SOFTWARE_VERSION     NA
}
COMPLETION
{
    NUMBER          877
    VERSION         4
    CALIBRATION_VERSION 1
    CONFIGURATION_ID    877    
}
REPLICATE
{
    REPLICATE_ID            1985
    ASSAY_NUMBER            656
    ASSAY_VERSION           4
    ASSAY_STATUS            Research
    DILUTION_ID         1
}
REPLICATE
{
    REPLICATE_ID            1985
    ASSAY_NUMBER            656
    ASSAY_VERSION           4
    ASSAY_STATUS            Research
}

Code:

static IEnumerable<IDictionary<string, string>> ReadParts(string path)
{
    using (var reader = File.OpenText(path))
    {
        var current = new Dictionary<string, string>();
        string line;
        while ((line = reader.ReadLine()) != null)
        {
            if (string.IsNullOrWhiteSpace(line)) continue;

            if (line.StartsWith("REPLICATE"))
            {
                yield return current;
                current = new Dictionary<string, string>();
            }
            else
            {
                var parts = line.Split('\t');
            }

            if (current.Count > 0) yield return current;
        }
    }
}

public static void parseFile(string fileName)
    {
        foreach (var part in ReadParts(fileName))
        {
           //part["fIELD1"] will retireve certain values from the REPLICATE PART HERE
        }
    }

Answer 1

If you add a yield return current; after your while loop is over, you will get the final dictionary.

I believe it would be better to check for ‘}’ as an end to the current block, and then put the yield return there. although you can’t use regex t parse the entire file, you can use regex to search for the key-value pairs within the lines. The following iterator code should work. It will only return dictonaries for REPLICATE blocks.

 // Check for lines that are a key-value pair, separated by whitespace.
// Note that value is optional
static string partPattern = @"^(?<Key>\w*)(\s+(?<Value>\.*))?$";

static IEnumerable<IDictionary<string, string>> ReadParts(string path)
{
    using (var reader = File.OpenText(path))
    {
        string line;
        while ((line = reader.ReadLine()) != null)
        {
            // Ignore lines that just contain whitespace
            if (string.IsNullOrWhiteSpace(line)) continue; 

            // This is a new replicate block, start a new dictionary
            if (line.Trim().CompareTo("REPLICATE") == 0)
            {
                yield return parseReplicateBlock(reader);
            }
        }
    }
}

private static IDictionary<string, string> parseReplicateBlock(StreamReader reader)
{
    // Make sure we have an opening brace
    VerifyOpening(reader);
    string line;
    var currentDictionary = new Dictionary<string, string>();
    while ((line = reader.ReadLine()) != null)
    {
        // Ignore lines that just contain whitespace
        if (string.IsNullOrWhiteSpace(line)) continue;

        line = line.Trim();

        // Since our regex used groupings (?<Key> and ?<Value>), 
        // we can do a match and check to see if our groupings 
        // found anything. If they did, extract the key and value. 
        Match m = Regex.Match(line, partPattern);
        if (m.Groups["Key"].Length > 0)
        {
            currentDictionary.Add(m.Groups["Key"].Value, m.Groups["Value"].Value);
        }
        else if (line.CompareTo("}") == 0)
        {
            return currentDictionary;
        }
    }
    // We exited the loop before we found a closing brace, throw an exception
    throw new ApplicationException("Missing closing brace");
}

private static void VerifyOpening(StreamReader reader)
{
    string line;
    while ((line = reader.ReadLine()) != null)
    {
        // Ignore lines that just contain whitespace
        if (string.IsNullOrWhiteSpace(line)) continue;

        if (line.Trim().CompareTo("{") == 0)
        {
            return;
        }
        else
        {
            throw new ApplicationException("Missing opening brace");
        }
    }
    throw new ApplicationException("Missing opening brace");
}

Update: I made sure that the regex string includes cases where there is no value. In addition, the group indexes were all changed to use the group name to avoid any issues if the regex string is modified.