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C#: Export a List of Objects to CSV with LINQ, Attributes, and Generics

Greg — Thu, 26 Jan 2012 03:00:48 +0000

Have you ever needed to transform data from in-memory C# objects to a CSV flat-file of a specific format? Here’s an easy way to get the job done with C#, LINQ, and Generics.

First you need the Attribute you will use to mark up the properties on your exportable class:

///

/// The name of the column for the CSV
/// generated by a list of objects with
/// properties marked with this attribute,
/// if Export is true. Uses Order to order
/// the properties on export
///

public class CsvColumnNameAttribute : Attribute
{
public bool Export { get; set; }
public int Order { get; set; }
public string Name { get; set; }

public CsvColumnNameAttribute()
{
Export = true;
Order = int.MaxValue; // so unordered columns are at the end
}

}

And here is how you use the attributes to mark up your class so you can export a list of instantiated objects:

public class MyClassToExport
{
[CsvColumnAttribute(Name = "Activation Date", Order = 1)]
public DateTime Date { get; set; }

[CsvColumnAttribute(Name = "Full Name", Order = 2)]
public string User { get; set; }

[CsvColumnAttribute(Name = "Account Type", Order = 3)]
public int Level { get; set; }

[CsvColumnAttribute(Name = "Account Action", Order = 4)]
public string Action { get; set; }

[CsvColumnAttribute(Export = false)]
public DateTime Added { get; set; }
}

Then you need to code to actually create the CSV using LINQ and Generics:

///

/// Generate a CSV as a string from a list
/// of objects that have the CsvColumnNameAttribute
/// applied
///

public string GetCsv<T>(List<T> csvDataObjects)
{
PropertyInfo[] propertyInfos = typeof(T).GetProperties();
var sb = new StringBuilder();
sb.AppendLine(GetCsvHeaderSorted(propertyInfos));
csvDataObjects.ForEach(d => sb.AppendLine(GetCsvDataRowSorted(d, propertyInfos)));
return sb.ToString();
}

private string GetCsvDataRowSorted<T>(T csvDataObject, PropertyInfo[] propertyInfos)
{
IEnumerable<string> valuesSorted = propertyInfos
.Select(x => new
{
Value = x.GetValue(csvDataObject, null),
Attribute = (CsvColumnNameAttribute)Attribute.GetCustomAttribute(x, typeof(CsvColumnNameAttribute), false)
})
.Where(x => x.Attribute != null && x.Attribute.Export)
.OrderBy(x => x.Attribute.Order)
.Select(x => GetPropertyValueAsString(x.Value));
return String.Join(",", valuesSorted);
}

private string GetCsvHeaderSorted(PropertyInfo[] propertyInfos)
{
IEnumerable<string> headersSorted = propertyInfos
.Select(x => (CsvColumnNameAttribute)Attribute.GetCustomAttribute(x, typeof(CsvColumnNameAttribute), false))
.Where(x => x != null && x.Export)
.OrderBy(x => x.Order)
.Select(x => x.Name);
return String.Join(",", headersSorted);
}

private string GetPropertyValueAsString(object propertyValue)
{
string propertyValueString;

if (propertyValue == null)
propertyValueString = "";
else if (propertyValue is DateTime)
propertyValueString = ((DateTime)propertyValue).ToString("dd MMM yyyy");
else if (propertyValue is int)
propertyValueString = propertyValue.ToString();
else if (propertyValue is float)
propertyValueString = ((float)propertyValue).ToString("#.####"); // format as you need it
else if (propertyValue is double)
propertyValueString = ((double)propertyValue).ToString("#.####"); // format as you need it
else // treat as a string
propertyValueString = @"""" + propertyValue.ToString().Replace(@"""", @"""""") + @""""; // quotes with 2 quotes

return propertyValueString;
}

Once you have that code up in going in your application, you can export your list of objects to a CSV with just a couple lines of code:

// example usage
var export = new List<MyClassToExport>();
// TODO add items to list :)
var csv = GetCsv(export);

Hope this helps! And let me know if you have any suggestions or improvements.

C# : String Extension to Parse Enums

Greg — Fri, 23 Sep 2011 15:30:48 +0000

It seems to me that there is too much typing involved in parsing a string as an Enum type. Here’s a quick string extension method to turn it into a simpler one liner:

public static T EnumParse<T>(this string input, bool ignoreCase = true)
{
return (T)Enum.Parse(typeof(T), input, ignoreCase);
}

With this extension, you can now do this:

string s = "MyEnumValue";
MyEnum e = s.EnumParse<MyEnum>();

Seems shorter to me.

ASP.Net MVC: Partially Secured Sites / Switching from HTTPS back to HTTP

Greg — Tue, 06 Sep 2011 16:47:20 +0000

Most sites out there have some portions that should be only served via HTTPS, while the remainder can be HTTP, such as account pages and content pages respectively. This is sometimes called a “partially secured site.”

Starting with MVC 2, you could decorate controllers and actions with the RequireHttps attribute, which would redirect non-secure GET requests to HTTPS. Unfortunately, once you are in HTTPS, you won’t automatically switch back to HTTP for those actions that do not require it.

To do that, you can override OnActionExecuting in your base controller (to save you from having to reimplement the call in each of your actual controllers) and redirect the user.

Here’s the code

[RequireHttps]
public ActionResult MySslAction()
{
// HTTPS
}

public ActionResult MyNonSslAction()
{
// HTTP
}

protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
if (filterContext.HttpContext.Request.IsSecureConnection && !filterContext.ActionDescriptor.IsDefined(typeof(RequireHttpsAttribute), true))
{
// redirect to un-secured page
string url = "http://" + filterContext.HttpContext.Request.Url.Host + filterContext.HttpContext.Request.RawUrl;
filterContext.HttpContext.Response.Redirect(url);
}

base.OnActionExecuting(filterContext);
}

C#: String Extension to Replace Accented Characters

Greg — Fri, 29 Apr 2011 13:47:39 +0000

Have you ever wanted to replace “accented” characters in a string with their equivalent English character? Here’s a string extension that replaces these diacritics within a string for C# 2.0 and up:

public static string ReplaceDiacritics(this string source)
{
string sourceInFormD = source.Normalize(NormalizationForm.FormD);

var output = new StringBuilder();
foreach (char c in sourceInFormD)
{
UnicodeCategory uc = CharUnicodeInfo.GetUnicodeCategory(c);
if (uc != UnicodeCategory.NonSpacingMark)
output.Append(c);
}

return (output.ToString().Normalize(NormalizationForm.FormC));
}

The extension replaces characters like “ö” with “o”, “è″ with “e” and “ñ” with “n”. This is great for getting acceptable URLs or for auto-complete / type-ahead search boxes where you want to match on both the accented and non-accented characters.

Creating a SQL CLR User Defined Function

Greg — Mon, 07 Mar 2011 20:28:07 +0000

Starting with SQL Server 2005, Microsoft added the awesome ability to reference .Net assemblies from your T-SQL procedures. Here’s a quick 5 step overview on how to get up and running with your code-based User Defined Function.

1) Create a project from the Visual C# SQL CLR Database Project template (just so you can get the correct references and get a test harness going).

2) Add a class containing your UDFs. This one does a basic Regular Expression comparison:

public class MyUdf
{
[Microsoft.SqlServer.Server.SqlFunction(IsDeterministic = true)]
public static SqlBoolean FnRegExMatch(string source, string pattern)
{
Match m = Regex.Match(source, pattern,
RegexOptions.CultureInvariant |
RegexOptions.IgnoreCase |
RegexOptions.Singleline
);
return m.Success;
}
}

3) Enable the CLR on your SQL Server instance through the configuration options:

EXEC sp_configure 'show advanced options' , '1'
GO
RECONFIGURE
GO
EXEC sp_configure 'clr enabled' , '1'
GO
RECONFIGURE
GO
EXEC sp_configure 'show advanced options' , '0';
GO

4) Add the assembly and then create a reference to your UDF:

CREATE ASSEMBLY [MyUdfs]
AUTHORIZATION [dbo]
FROM 'C:\SqlServerClr\MyUdf.dll'
WITH PERMISSION_SET = SAFE -- we only have "safe" calls in our lib
GO

CREATE FUNCTION [dbo].[FnRegExMatch](
@SOURCE nvarchar(4000),
@pattern nvarchar(4000)
)
RETURNS BIT
WITH EXECUTE AS CALLER
AS
EXTERNAL NAME [MyUdf].[FnRegExMatch]
GO

5) Now you should be able to call your function:

SELECT dbo.FnRegExMatch('my test string', '\btest\b')

Of course this is just the barest of essentials to get you going with SQL CLR UDFs, but I hope it helps!

Retrieve Image from Windows Clipboard via .Net C#

Greg — Mon, 02 Nov 2009 21:32:34 +0000

If you want to snag clipboard data from a different application into the context of your running .Net application, here’s how you can do it:

private static Image _clipBoardImage = null;

private static Image GetImageFromCopyPasteBuffer()
{
Thread t = new Thread(new ThreadStart(GetClipboardBitmap));
t.SetApartmentState(ApartmentState.STA);
t.Start();
t.Join();
return _clipBoardImage;
}

private static void GetClipboardBitmap()
{
IDataObject data = Clipboard.GetDataObject();
if (data == null || !data.GetDataPresent(DataFormats.Bitmap, true))
throw new ApplicationException("No clipboard image data was present.");
_clipBoardImage = (Image)data.GetData(DataFormats.Bitmap);
}

Hope this helps!

.Net Friend Assemblies

Greg — Wed, 21 Oct 2009 19:02:19 +0000

Have you ever want to create a “friend” assembly while programming with the .Net framework? They can be very useful for segmenting your codebase amongst different projects.

Friend Assemblies allow an assembly to see the internal methods and properties of a different assembly by specifying an attribute on the primary assembly that specifies the assembly name of the friend.

The simplest way to do this is to add something like the following to your AssemblyInfo.cs file in your primary project:

[assembly: InternalsVisibleTo("my.friend.assembly")]

This would allow my.friend.assembly to have access to all of the primary project’s internals.

If you need to worry about security of the assemblies (I suppose we all should), then you should also consider using strong names in conjunction with the compiler attribute.

More information on .Net Friend Assemblies can be found here:

http://msdn.microsoft.com/en-us/library/0tke9fxk.aspx

Hope this helps!

JavaScript, UTF-8 Encoding: escape() vs. encodeURIComponent()

Greg — Thu, 06 Aug 2009 23:07:00 +0000

ASP.Net web applications default to UTF-8 encoding. Now, if you are using JavaScript to create or change URLs, you might run into an issue with the way the function “escape()” encodes characters if you are handling the decoding in your code behind via Request.QueryString.

To avoid ending up with “unkown” characters in your resultant string, use the JavaScript function “encodeURIComponent()” instead. This should correctly encode your URLs for UTF-8.

Convert Hex to Readable String and Readable Text to Hex

Greg — Tue, 23 Jun 2009 22:24:16 +0000

If you ever need to convert Hex data to readable strings or the reverse, try the following methods:

private static readonly char[] HexChars = "0123456789ABCDEF".ToCharArray();

private static string ConvertToHex(string ascii)
{
if (ascii == null) return null;
if (ascii == "") return "";

byte[] bytes = Encoding.UTF8.GetBytes(ascii);

StringBuilder converted = new StringBuilder(bytes.Length * 2);

foreach (byte b in bytes)
{
converted.Append(HexChars[b >> 4]);
converted.Append(HexChars[b & 0xf]);
}

return converted.ToString();
}

private static string ConvertFromHex(string hex)
{
if (hex == null) return null;
if (hex == "") return "";
if (hex.Length % 2 != 0)
throw new ApplicationException("hex string length should be divisble by 2: " + hex);

byte[] bytes = new byte[hex.Length / 2];

for (int i = 0; i < bytes.Length; i++)
bytes[i] = byte.Parse(hex[2 * i] + "" + hex[2 * i + 1], NumberStyles.HexNumber);

string converted = Encoding.UTF8.GetString(bytes);

if (converted[converted.Length - 1] == '\0')
converted = converted.Remove(converted.Length - 1, 1);

return converted;
}

I have found this is very useful for parsing binary data from Active Directory sources such as “csvde”.

Hope this helps you out! Let me know if you know of a better/faster method – it is always appreciated.

Read a CSV file with Regular Expressions in .Net

Greg — Tue, 23 Jun 2009 18:51:17 +0000

Here’s how you can read a CSV file using Regular Expressions in .Net:

p>
public static DataTable GetDataTableFromCsvFile(string file)
{
// Where the CSV data goes
DataTable dt = new DataTable("CsvData");

// The pattern used to parse the CSV
const string csvPattern = ",(?=(?:[^\"]*\"[^\"]*\")*(?![^\"]*\"))";
Regex csvRegex = new Regex(csvPattern);

// Read all lines in the file
// (not great for large files)
string[] fileLines = File.ReadAllLines(file);

// Get the column headers
// (assumes first row has headers and that
// each column contains string values and
// that each column name is unique)

Dictionary<int, string> headers = new Dictionary<int, string>();
string[] headerValues = csvRegex.Split(fileLines[0]);

for (int i = 0; i < headerValues.Length; i++)
{
headers.Add(i, headerValues[i]);
dt.Columns.Add(new DataColumn(headerValues[i], typeof (string)));
}

// Then add the the rest of the lines
for (int k = 1; k < fileLines.Length; k++)
{

DataRow dr = dt.NewRow();

string line = fileLines[k];
string[] cols = csvRegex.Split(line);

for (int i = 0; i < cols.Length; i++)
{
string header = headers[i];
string data = cols[i];

// remove quotes around the field
if (data.Length > 1 && data.StartsWith("\"") && data.EndsWith("\""))
data = data.Remove(data.Length - 1, 1).Remove(0, 1);

dr[header] = data;
}

dt.Rows.Add(dr);
}

return dt;
}

Of course, you will need to add in error catching and handling as well.

Hope this helps!