Question

Using: ado.net
How can I select data from a DataTable using SQL with an aggregation function?
I know that I can use select property (http://msdn.microsoft.com/en-us/library/t5ce3dyt(vs.71).aspx ) but I need an aggregation function to use it with, and I didn’t find any examples for this.

Answer 1

Aggregates in DataSet are normally used in conjunction with relations:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemdatadatacolumnclassexpressiontopic.asp

Basically if you need your result as single row with single column, you’d need to create that extra table with that column and add expression to it so you would get a single row:

Table1, column Number: 3 rows containing 1,2,3

Table2, column Average, expression set to “Avg(Table1.Number)”: One rows containing 2

As to your particular example: “SELECT COUNT(*) FROM “, you could use row count: table.Rows.Count

You can also create DataView with particular filter and get number of rows in it to emulate more complex cases of COUNT.