LINQ allows to perform various queries against different data structures. Wouldn’t it be great if you could easily export result of a LINQ query to CSV? Fortunately you can! This article by Scott Hanselman explain how and culminates in cool in its simplicity code:
namespace FooFoo
{
public static class LinqToCSV
{
public static string ToCsv<T>(this IEnumerable<T> items)
where T : class
{
var csvBuilder = new StringBuilder();
var properties = typeof(T).GetProperties();
foreach (T item in items)
{
string line = string.Join(",",properties.Select(p => p.GetValue(item, null).ToCsvValue()).ToArray());
csvBuilder.AppendLine(line);
}
return csvBuilder.ToString();
}
private static string ToCsvValue<T>(this T item)
{
if(item == null) return "\"\"";
if (item is string)
{
return string.Format("\"{0}\"", item.ToString().Replace("\"", "\\\""));
}
double dummy;
if (double.TryParse(item.ToString(), out dummy))
{
return string.Format("{0}", item);
}
return string.Format("\"{0}\"", item);
}
}
}
This code adds .ToCsv() extension method to any IEnumerable so you can run something like
Language Integrated Query (LINQ) is a cool feature of .NET languages like C# that allows you to perform SQL-like query right within the language against language’s data structures (lists, arrays etc.) But one drawback of LINQ – you have to know in advance, at compile time which fields to select, what filter conditions would be. Sometimes there’s a need to supply these at runtime – e.g. user selects which fields they want to see
Thankfully there exists Dynamic LINQ Library that allows you to supply LINQ parameters as a string akin Dynamic SQL. Here’s an example of such query from the library’s homepage:
var query = db.Customers
.Where("City == @0 and Orders.Count >= @1", "London", 10)
.OrderBy("CompanyName")
.Select("new(CompanyName as Name, Phone)");
Now, one thing that LINQ can do is query XML. So in theory if we load, say, this XML:
Pebble Time timeline is a very cool user interface allowing you to see future and past events and act upon them right on your watch. Right out of the box Pebble Time supports calendar pins that shows your future and past appointments in the timeline as well as weather alerts. But the real power comes from 3rd party apps using timeline – they can add anything from sports scores to latest news to TV showtimes – limit is just your imagination.
Pebble has always had open SDK – this is one of its major strengths, and Timeline is not an exception. Timeline API is a very straightforward way to push your own pins to users of your app. There’re various examples and libraries including PHP and node.js on how to deal with the timeline, but I, being mostly a Microsoft developer by trade, decided to bring Timeline into .NET. This particular example is in ASP.NET – pin is pushed from Webpage when user clicks a button, but it’s just one of the possible scenarios.
In order to push timeline pins successfully you will need 2 pieces:
A watchapp that runs on Pebble. In fact after first run, that subscribes user to timeline, the app doesn’t have to be running on the watch anymore. It doesn’t even have to be on the watch. As long as it simple remains in your locker on the phone – you will continue to receive its pins
Your own server that sends calls to Pebble public Timeline API to control pins
If you’re trying to retrieve distinct rows from your ADO.NET data table using code like
From oRow As DataRow In dtTable.Rows Select oRow Distinct
or
(From oRow As DataRow In dtTable.Rows Select oRow).Distinct()
You may find that rows that are being return are not unique. That’s because by default LINQ compares table rows by reference. If you need to compare by actual values – use DataRowComparer in Distinct method call:
(From oRow As DataRow In dtTable.Rows Select oRow).Distinct(DataRowComparer.Default)
By default if server-side filtering is enabled in UltraWebGrid controls, it displays a small “funnel” icon in the column header, if you click this icon – a list of unique values from this column is displayed and selecting a value filters the grid by displaying only rows that have this value.
This default behavior works, sort of – it has many issues. If your grid has paging enabled – only values from the current page will be displayed. If your columns or values has characters that grid doesn’t like (commas, square brackets etc.) an exception will be thrown (this happens because under the hood grid converts your filters into a string that is passed to DataTable’s RowFilter), there’re other issues as well.
ADO.NET DataTable offers handy RowFilter property (via its DefaultView object), for example to filter by some string value and display filtered data in a grid a code like this is used:
where odtMyData is a DataTable object and odgDataGrid is a Data Grid.
This works well, but what if you need preprocess data in the DataTable prior comparing it to the filter value – what if you need to apply a user-defined function to it? In my case I had a VB function called ProcessTags which stripped HTML tags from a string, so for example strings like this:
<a href="http://someurl">This is a sample text</a>
and this
<span style="color:red">This is a </span><label>sample text</label>
would be converted into the same text
This is a sample text
So I needed to create condition that would return DataTable rows with that have both HTML values by comparing to "This is a sample text".
How? RowFilter‘s syntax is pretty poor and external function cannot be used, so something like
odtMyData.DefaultView.RowFilter = "ProcessTags(Field) = 'This is a sample text'"
odgDataGrid.DataSource = odtMyData
odgDataGrid.DataBind()
Today I needed to do a simple thing: Combine selected values of .NET CheckListBox control into a comma separated string. I am lazy, so I decided to Google for a ready-to-use piece of code. Sure enough there’re tons of those. But all of them involve looping through control items, checking IF item is selected, then adding values.. Boring, routine stuff.
People! We live in the 21st century, age of inspiration! Uhm.. sorry, got carried away. Bottom line: I didn’t like any of those solutions and being a fan of LINQ I put together one of my own. Continue reading 'CheckListBox to comma-separated string'»
Linq2Sql has a great use of stored procedures – it converts them into methods which you can easily call using standardized .NET syntax. For example if you have SP:
ALTER PROCEDURE MyProcedure(MyParam int) ...
after dragging it into Linq2Sql designer you can call it in your .NET code like this:
In the past I described how to perform string aggregates in T-SQL. In this post I will show how strings can be concatenated in LINQ.
I am using ADO.NET data table as a source for the query, but LINQ being LINQ can pull data pretty much from anything so this example can easily be adjusted.
First things first, let’s create the source. As in T-SQL post I am using ol’ faithful Northwind database and getting data from the Employees table:
Dim oConn As New SqlConnection(sMyConnStr) : oConn.Open()
Dim oComm As New SqlCommand("SELECT Country, FirstName FROM Employees ORDER BY Country, FirstName", oConn)
Dim oAd As New SqlDataAdapter(oComm) : Dim oTable As New DataTable : oAd.Fill(oTable)
This will fill the datatable with employees’ first names and countries
Country FirstName
UK Anne
UK Michael
UK Robert
UK Steven
USA Andrew
USA Janet
USA Laura
USA Margaret
USA Nancy
If you’re using Infragistics classic UltraWebGrid with LoadOnDemand not set and paging enabled, getting column filters to work can be tricky. By default clicking on Filter icon will display column data from current page only, ignoring other pages. To make it work you have to take matter in your own hands – populate filter data in code.
The best place to do it is in InitializeLayout event. There you can loop thru all the columns, calling function to populate column filters:
Protected Sub xMyGrid_InitializeLayout(ByVal sender As Object, ByVal e As LayoutEventArgs) Handles xMyGrid.InitializeLayout
For Each ugColumn As UltraGridColumn In e.Layout.Grid.Columns
GatherFilterDataForColumn(ugColumn)
Next
End Sub
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