Recently while working in my Data Access Layer (DAL) I pulled data from two different databases and combined them into a .Net DataTable before returning that DataTable to my business logic layer (BAL) for.. well business logic stuff. Since I could not find an AddAt() method for adding columns at a specific index I had to try and find a way to reorder columns after adding them. I found the solution on forums.asp.net and it’s actually very easy to do. Suppose you had a DataTable named ‘dt’ and column named ‘Staff Number’ which you wanted to be in at column/index 0 in your datatable. The following line of code is all it takes.
dt.Columns[“Staff Number”].SetOrdinal(0);The columns that follow ‘Staff Number’ will all shift across by 1. Incidentally DataTable.Columns[] has two overloads, one which takes a zero-based index of the column to return and another that takes the column name of the column to return. While accessing columns via index numbers is quicker it’s not recommended as it’s too difficult to maintain and read. Imagine for instance I had code which accessed various columns from the ‘dt’ DataTable via an index number and then I realised that I wanted my ‘Staff Number’ column to be first and thus set its index or Ordinal to 0, I would then have to change my index based statements for all columns that were shifted by 1. Since this has the potential to be a royal pain and since my development team would rather read dt.Columns[”COLUMNNAME”]; than dt.Columns[INDEXNUMBER]; I always recommend using Column names for accessing data from things like DataTables, DataSets and SQL statements.
The columns that follow ‘Staff Number’ will all shift across by 1. Incidentally DataTable.Columns[] has two overloads, one which takes a zero-based index of the column to return and another that takes the column name of the column to return. While accessing columns via index numbers is quicker it’s not recommended as it’s too difficult to maintain and read. Imagine for instance I had code which accessed various columns from the ‘dt’ DataTable via an index number and then I realised that I wanted my ‘Staff Number’ column to be first and thus set its index or Ordinal to 0, I would then have to change my index based statements for all columns that were shifted by 1. Since this has the potential to be a royal pain and since my development team would rather read than I always recommend using Column names for accessing data from things like DataTables, DataSets and SQL statements.
