Develop Reference

C# How to implement CSV file into this code

Hi I am fairly new to coding, I have a piece of code that searches for a string and replaces it with another string like so:
var replacements = new[]{
new{Find="123",Replace="Word one"},
new{Find="ABC",Replace="Word two"},
new{Find="999",Replace="Word two"},
};
var myLongString = "123 is a long 999 string yeah";
foreach(var set in replacements)
{
myLongString = myLongString.Replace(set.Find, set.Replace);
}
If I want to use a CSV file that contains a lot of words and their replacements, for example, LOL,Laugh Out Loud, and ROFL, Roll Around Floor Laughing. How would I implement that?

Create a text file that looks like (you could use commas, but I like pipes (|)):
123|Word One
ABC|Word Two
999|Word Three
LOL|Laugh Out Loud
ROFL|Roll Around Floor Laughing
Then create a tiny helper class:
public class WordReplace
{
public string Find { get; set; }
public string Replace { get; set; }
}
And finally, call this code:
private static string DoWordReplace()
{
//first read in the data
var fileData = File.ReadAllLines("WordReplace.txt");
var wordReplacePairs = new List<WordReplace>();
var lineNo = 1;
foreach (var item in fileData)
{
var pair = item.Split(new[] {'|'}, StringSplitOptions.RemoveEmptyEntries);
if (pair.Length != 2)
{
throw new ApplicationException($"Malformed file, line {lineNo}, data = [{item}] ");
}
wordReplacePairs.Add(new WordReplace{Find = pair[0], Replace = pair[1]});
++lineNo;
}
var longString = "LOL, 123 is a long 999 string yeah, ROFL";
//now do the replacements
var buffer = new StringBuilder(longString);
foreach (var pair in wordReplacePairs)
{
buffer.Replace(pair.Find, pair.Replace);
}
return buffer.ToString();
}
The result is:
Laugh Out Loud, Word One is a long Word Three string yeah, Roll Around Floor Laughing

Custom string format from list C#

i have a class with a list of data, like this:
public List<Data> data;
public class Data {
public String KEY;
public String VALUE;
}
My question is: How can i get the next format string with data of List<Data>?
{"key1":["value1"],"key2":["value2"]}
I tried with Newtonsoft.Json.JsonConvert but i get this string:
[{"KEY":"key1","VALUE":"value1"},{"KEY":"key1","VALUE":"value1"}]

If you want to easily use Json.Net, you just need to convert your List<Data> to a Dictionary<string, string> first:
var dict = data.ToDictionary<string, string[]>(d => d.KEY, d => new[] { d.VALUE });
JsonConvert.SerializeObject(dict);

this is an application of "to a man with a hammer, every problem looks like a nail"!
sincerly, Justin's answer is the most suitable, but I don't mind introduce this work around. (P.S: not tested it may need some troubleshooting)
private string convertToJSON(list<Data> data)
{
StringBuilder sb = new StringBuilder();
string str;
int i=0;
sb.Append("{"); // start
for(i=0; i<data.Count-1; i++)
{
// add each pair of data with a comma
str = String.Format("\"{0}\":[\"{1}\"], ", data[i].key, data[i].value);
sb.Append(str);
}
// add the last pair of data
sb.Append("\"{0}\":[\"{1}\"]", data[i+1].key, data[i+1].value);
sb.Append("}"); // close the sequence
string Result = sb.ToString(); // resulting string
return Result;
}
Then, just call it like this string json = convertToJSON(data);

Regular Expression with Lambda Expression

I've got several text files which should be tab delimited, but actually are delimited by an arbitrary number of spaces. I want to parse the rows from the text file into a DataTable (the first row of the text file has headers for property names). This got me thinking about building an extensible, easy way to parse text files. Here's my current working solution:
string filePath = #"C:\path\lowbirthweight.txt";
//regex to remove multiple spaces
Regex regex = new Regex(#"[ ]{2,}", RegexOptions.Compiled);
DataTable table = new DataTable();
var reader = ReadTextFile(filePath);
//headers in first row
var headers = reader.First();
//skip headers for data
var data = reader.Skip(1).ToArray();
//remove arbitrary spacing between column headers and table data
headers = regex.Replace(headers, #" ");
for (int i = 0; i < data.Length; i++)
{
data[i] = regex.Replace(data[i], #" ");
}
//make ready the DataTable, split resultant space-delimited string into array for column names
foreach (string columnName in headers.Split(' '))
{
table.Columns.Add(new DataColumn() { ColumnName = columnName });
}
foreach (var record in data)
{
//split into array for row values
table.Rows.Add(record.Split(' '));
}
//test prints correctly to the console
Console.WriteLine(table.Rows[0][2]);
}
static IEnumerable<string> ReadTextFile(string fileName)
{
using (var reader = new StreamReader(fileName))
{
while (!reader.EndOfStream)
{
yield return reader.ReadLine();
}
}
}
In my project I've already received several large (gig +) text files that are not in the format in which they are purported to be. So can I see having to write methods such as these with some regularity, albeit with a different regular expression. Is there a way to do something like
data =data.SmartRegex(x => x.AllowOneSpace) where I can use a regular expression to iterate over the collection of strings?
Is something like the following on the right track?
public static class SmartRegex
{
public static Expression AllowOneSpace(this List<string> data)
{
//no idea how to return an expression from a method
}
}
I'm not too overly concerned with performance, just would like to see how something like this works

You should consult with your data source and find out why your data is bad.
As for the API design that you are trying to implement:
public class RegexCollection
{
private readonly Regex _allowOneSpace = new Regex(" ");
public Regex AllowOneSpace { get { return _allowOneSpace; } }
}
public static class RegexExtensions
{
public static IEnumerable<string[]> SmartRegex(
this IEnumerable<string> collection,
Func<RegexCollection, Regex> selector
)
{
var regexCollection = new RegexCollection();
var regex = selector(regexCollection);
return collection.Select(l => regex.Split(l));
}
}
Usage:
var items = new List<string> { "Hello world", "Goodbye world" };
var results = items.SmartRegex(x => x.AllowOneSpace);

How to build WebClient querystring with duplicate keys?

I'm posting data to a service that requires that I submit duplicate query string keys (ugly and not specified in any standards).
I'm using WebClient object to build the request. I'd like to keep using it since it is used frequently elsewhere in the project.
When I do this
foreach(var f in formats)
client.QueryString.Add("formats", f);
I get a list &formats=format_1,format_2,format_3 which the service does not support.
Is there a better alternative than this old-school ugliness:
var extraQueryString = string.Empty;
extraQueryString += "?apiKey=" + TRANSCODE_KEY;
extraQueryString += "&fileKey=" + fileKey;
foreach (var f in formats)
extraQueryString += "&formats=" + f;
var response = client.UploadData(TRANSCODE_URI + "task" + extraQueryString , new byte[] { });

The reason for this is because the NameValueCollection separates duplicate keys with commas. You could extend the NameValueCollection and override the Get method and have it return the format you want.
public class DupeNVC: NameValueCollection
{
private string _duplicateKey;
public DupeNVC(string duplicateKey = null)
{
_duplicateKey = duplicateKey;
}
public override string Get(int index)
{
//check if duplicate key has been specified
//if not, then call the default Get implementation
if (!String.IsNullOrEmpty(_duplicateKey))
{
ArrayList list = (ArrayList)base.BaseGet(index);
int num = (list != null) ? list.Count : 0;
if (num == 1)
{
return (string)list[0];
}
if (num > 1)
{
StringBuilder stringBuilder = new StringBuilder((string)list[0]);
for (int i = 1; i < num; i++)
{
//format our string and append the duplicate key specified
stringBuilder.AppendFormat("&{0}=", _duplicateKey);
stringBuilder.Append((string)list[i]);
}
return stringBuilder.ToString();
}
return null;
}
else
return base.Get(index);
}
}
You can use it like a normal NameValueCollection but if you pass in a duplicate strning in the constructor, it will look for that duplicate key and run the modified code above (otherwise it will just use the default base.Get method.
DupeNVC dnvc = new DupeNVC("formats");
foreach(var f in formats)
dnvc.Add("formats", f);
webClient.QueryString = dnvc;
This hasn't been fully tested but it should output the querystring format you want. Of course, this could be extended further by taking a collection of duplicate keys but this was just to give you an idea for your current problem.

Here's my take on this. WebClient essentially works like the ToString method of this class; it gets all the keys and then retrieves the values one at a time, doing a concatenate. So I override the AllKeys to return an array with repeated elements..
For example if a particular key has multiple values:
nvc["hello"] = { "a", "b", "c" }
Then my AllKeys will return an array with "hello" 3 times. WebClient will naively request it 3 times. A Dictionary tracks how many times a "hello" has been requested, and returns a different one each time (pseudo enumerator)
public class ParrotingNameValueCollection : NameValueCollection
{
Dictionary<string, int> _indexTracker = new Dictionary<string, int>();
public override string[] AllKeys
{
get
{
var l = new List<string>();
foreach (var k in base.AllKeys)
{
foreach (var x in (ArrayList)base.BaseGet(k))
l.Add(k);
_indexTracker[k] = 0;
}
return l.ToArray();
}
}
public override string Get(string name)
{
var list = (ArrayList)base.BaseGet(name);
var toReturn = (string)list[_indexTracker[name]];
_indexTracker[name]++;
return toReturn;
}
public override string ToString()
{
string delimiter = String.Empty;
StringBuilder values = new StringBuilder();
foreach (string name in this.AllKeys)
{
values.Append(delimiter);
values.Append((name));
values.Append("=");
values.Append((this[name]));
delimiter = "&";
}
return values.ToString();
}
}

Join collection of objects into comma-separated string

In many places in our code we have collections of objects, from which we need to create a comma-separated list. The type of collection varies: it may be a DataTable from which we need a certain column, or a List<Customer>, etc.
Now we loop through the collection and use string concatenation, for example:
string text = "";
string separator = "";
foreach (DataRow row in table.Rows)
{
text += separator + row["title"];
separator = ", ";
}
Is there a better pattern for this? Ideally I would like an approach we could reuse by just sending in a function to get the right field/property/column from each object.

string.Join(", ", Array.ConvertAll(somelist.ToArray(), i => i.ToString()))

static string ToCsv<T>(IEnumerable<T> things, Func<T, string> toStringMethod)
{
StringBuilder sb = new StringBuilder();
foreach (T thing in things)
sb.Append(toStringMethod(thing)).Append(',');
return sb.ToString(0, sb.Length - 1); //remove trailing ,
}
Use like this:
DataTable dt = ...; //datatable with some data
Console.WriteLine(ToCsv(dt.Rows, row => row["ColName"]));
or:
List<Customer> customers = ...; //assume Customer has a Name property
Console.WriteLine(ToCsv(customers, c => c.Name));
I don't have a compiler to hand but in theory it should work. And as everyone knows, in theory, practice and theory are the same. In practice, they're not.

I found string.Join and lambda Select<Func<>> helps to write minimum code.
List<string> fruits = new List<string>();
fruits.Add("Mango");
fruits.Add("Banana");
fruits.Add("Papaya");
string commaSepFruits = string.Join(",", fruits.Select(f => "'" + f + "'"));
Console.WriteLine(commaSepFruits);
List<int> ids = new List<int>();
ids.Add(1001);
ids.Add(1002);
ids.Add(1003);
string commaSepIds = string.Join(",", ids);
Console.WriteLine(commaSepIds);
List<Customer> customers = new List<Customer>();
customers.Add(new Customer { Id = 10001, Name = "John" });
customers.Add(new Customer { Id = 10002, Name = "Robert" });
customers.Add(new Customer { Id = 10002, Name = "Ryan" });
string commaSepCustIds = string.Join(", ", customers.Select(cust => cust.Id));
string commaSepCustNames = string.Join(", ", customers.Select(cust => "'" + cust.Name + "'"));
Console.WriteLine(commaSepCustIds);
Console.WriteLine(commaSepCustNames);
Console.ReadLine();

// using System.Collections;
// using System.Collections.Generic;
// using System.Linq
public delegate string Indexer<T>(T obj);
public static string concatenate<T>(IEnumerable<T> collection, Indexer<T> indexer, char separator)
{
StringBuilder sb = new StringBuilder();
foreach (T t in collection) sb.Append(indexer(t)).Append(separator);
return sb.Remove(sb.Length - 1, 1).ToString();
}
// version for non-generic collections
public static string concatenate<T>(IEnumerable collection, Indexer<T> indexer, char separator)
{
StringBuilder sb = new StringBuilder();
foreach (object t in collection) sb.Append(indexer((T)t)).Append(separator);
return sb.Remove(sb.Length - 1, 1).ToString();
}
// example 1: simple int list
string getAllInts(IEnumerable<int> listOfInts)
{
return concatenate<int>(listOfInts, Convert.ToString, ',');
}
// example 2: DataTable.Rows
string getTitle(DataRow row) { return row["title"].ToString(); }
string getAllTitles(DataTable table)
{
return concatenate<DataRow>(table.Rows, getTitle, '\n');
}
// example 3: DataTable.Rows without Indexer function
string getAllTitles(DataTable table)
{
return concatenate<DataRow>(table.Rows, r => r["title"].ToString(), '\n');
}

In .NET 4 you can just do string.Join(", ", table.Rows.Select(r => r["title"]))

You could write a function that transforms a IEnumerable<string> into a comma-separated string:
public string Concat(IEnumerable<string> stringList)
{
StringBuilder textBuilder = new StringBuilder();
string separator = String.Empty;
foreach(string item in stringList)
{
textBuilder.Append(separator);
textBuilder.Append(item);
separator = ", ";
}
return textBuilder.ToString();
}
You can then use LINQ to query your collection/dataset/etc to provide the stringList.

As an aside: The first modification I would make is to use the StringBuilder Class instead of just a String - it'll save resources for you.

I love Matt Howells answer in this post:
I had to make it into an extension:
public static string ToCsv<T>(this IEnumerable<T> things, Func<T, string> toStringMethod)
Usage (I am getting all the emails and turning them into a CSV string for emails):
var list = Session.Find("from User u where u.IsActive = true").Cast<User>();
return list.ToCsv(i => i.Email);

For collections you can use this method as well, for example:
string.Join(", ", contactsCollection.Select(i => i.FirstName));
You can select any property that you want to separate.

string strTest = "1,2,4,6";
string[] Nums = strTest.Split(',');
Console.Write(Nums.Aggregate<string>((first, second) => first + "," + second));
//OUTPUT:
//1,2,4,6

Here's my favorite answer adapted to the question,
and corrected Convert to ConvertAll:
string text = string.Join(", ", Array.ConvertAll(table.Rows.ToArray(), i => i["title"]));