Question

I have a DataTable dt with 2 columns. First col (call it CustomerId) is unique and doesn’t allow nulls. the second one allows nulls and is not unique.

From a method I get a CustomerId and then I would like to either insert a new record if this CustomerId doesn’t exist or increment by 1 what’s in the second column corresponding to that CustomerId if it exists.

I’m not sure how I should approach this. I wrote a select statement (which returns System.Data.DataRow) but I don’t know how to test whether it returned an empty string.

Currently I have:

//I want to insert a new row
if (dt.Select("CustomerId ='" + customerId + "'") == null) //Always true :|
    {
        DataRow dr = dt.NewRow();
        dr["CustomerId"] = customerId; 
    }

Answer 1

If the datatable is being populated by a database. I would recommend making the customerid a identity column. That way when you add a new row it will automatically create a new customerid which will be unique and 1 greater than the previous id (depending on how you setup your identity column)

I would check the row count which is returned from the select statement. Something like

I would also use string.Format…

So it would look like this

var selectStatement = string.Format("CustomerId = {0}", customerId);
var rows = dt.Select(selectStatement);
if (rows.Count < 1){
  var dr = dt.NewRow();
  dr["CustomerId"] = customerId; 
}