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A simple, lightweight and maintainable way to output arbitrary CSV/TSV - keeps header names close to the column/value definition.
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| // vars to be used inside column value funcs | |
| DateTime utcnow = DateTime.UtcNow; | |
| const decimal VIP_SPEND = 1000000M; | |
| var fields = new CsvDefinition<MyRecord> | |
| { | |
| { "Username", row => string.Concat(row.Prefix, ":", row.Username) }, | |
| { "Email", row => row.Email }, | |
| { "Status", row => row.TotalSpend >= VIP_SPEND ? "VIP" : "Pffft..., Peon" }, | |
| { "Spend ($)", row => row.TotalSpend == null ? "None" : row.TotalSpend.ToString("n2") }, | |
| { "Year of Birth", row => row.Yob > 1900 && row.Yob <= utcnow.Year ? row.Yob.Value.ToString() : null }, | |
| { "Enabled", row => row.IsEnabled ? "Y" : "N" }, | |
| { "Flags", row => string.Join(", ", new string[] | |
| { | |
| row.IsDemo ? "demo" : null, | |
| row.IsManager ? "manager" : null, | |
| row.IsAdmin ? "admin" : null | |
| }.Where(x => x != null)) | |
| }, | |
| { "Timestamp", row => DateTime.UtcNow.ToString("yyyy-MM-dd HH:mm:ss.fff") } | |
| }; | |
| IEnumerable<MyRecord> rows = someDataSource.AsEnumerable<MyRecord>(); | |
| using (var writer = new StringWriter()) | |
| { | |
| // perhaps write out some additional notes or headers | |
| // writer.WriteLine("# -- bof --") | |
| fields.Write(writer, rows, "\t"); // tab delimited | |
| // writer.WriteLine("# -- eof --") | |
| return writer.ToString(); | |
| } |
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| class CsvDefinition<T> : List<KeyValuePair<string, Func<T, string>>> | |
| { | |
| public CsvDefinition() | |
| : base() | |
| { } | |
| public CsvDefinition(int capacity) | |
| : base(capacity) | |
| { } | |
| public CsvDefinition(IEnumerable<KeyValuePair<string, Func<T, string>>> items) | |
| : base(items) | |
| { } | |
| /// <summary> | |
| /// Adds a Key/Value pair to the definition - used for easy object initialisation | |
| /// </summary> | |
| /// <param name="key">The name of the column/header</param> | |
| /// <param name="value">The Func to convert T into a string for the column value</param> | |
| public void Add(string key, Func<T, string> value) | |
| { | |
| Add(new KeyValuePair<string, Func<T, string>>(key, value)); | |
| } | |
| /// <summary> | |
| /// Writes the CSV, outputs a header line, then iterates over rows, converting into column values using the defined func | |
| /// </summary> | |
| /// <param name="writer">The TextWriter to write the lines to</param> | |
| /// <param name="rows">The enumerable of T tothat represents the lines</param> | |
| /// <param name="delimiter">The string to delimit column values with. A single character delimiter isare also used to escape the value, multi-character strings are not escaped.</param> | |
| public void Write(TextWriter writer, IEnumerable<T> rows, string delimiter = ",") | |
| { | |
| if(delimiter == null) | |
| throw new ArgumentNullException("delimiter"); | |
| char[] escChars = delimiter.Length == 1 ? new[] { delimiter[0], '\n', '\r', '"' } : new[] { '\n', '\r', '"' }; | |
| string header = string.Join(delimiter, this.Select(x => escape(x.Key, escChars))); | |
| writer.WriteLine(header); | |
| foreach (T row in rows) | |
| { | |
| string line = string.Join( | |
| delimiter, | |
| this.Select(x => escape(x.Value(row), escChars)) // x.Value == Func<T, string> | |
| ); | |
| writer.WriteLine(line); | |
| } | |
| } | |
| // adapted from: http://www.asp.net/web-api/overview/formats-and-model-binding/media-formatters | |
| static string escape(string value, char[] chars) | |
| { | |
| if (value == null) | |
| return null; | |
| if (value.IndexOfAny(chars) != -1) | |
| return string.Concat("\"", value.Replace("\"", "\"\""), "\""); | |
| return value; | |
| } | |
| } |
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