Question

I have some DataTables loaded into memory from various sources (SQL and MS Access), and each dataset has several columns, with only a subset of columns that are the same between each dataset. I’m working on some data synchronization code, and I want to compare these data tables, but only compare them based on the columns they have in common. If I had to I could probably do this with lots of loops, but I want to get more comfortable with LINQ and have more concise code.

Thus far I’ve managed to get a list of column names from each datatable, and used Intersect to get the list of column names common to both of them, like this:

private string[] Common_ColumnNames {
    get {
        // get column names from source & destination data
        string[] src_columnNames = 
        (from dc in _srcDataTable.Columns.Cast<DataColumn>() 
        select dc.ColumnName).ToArray();

        string[] dest_columnNames = 
        (from dc in _destDataTable.Columns.Cast<DataColumn>() 
        select dc.ColumnName).ToArray();

        // find the column names common between the two data sets 
        // - these are the columns to be compared when synchronizing
        return src_columnNames.Intersect( dest_columnNames ).ToArray();                
    }
}

Now I’m stuck… I need to select all rows from each DataTable, but only with those common columns. In my head I see this working a couple different ways:

1) select all rows from a datatable, and passing in my desired column list string[] variable to tell LINQ what columns I want

2) select all rows from a datatable, and use some lambda function (also fairly new to me) to remove the unwanted columns from each row, and outputing a new datatable with some dropped columns.

Any advice/suggestions on how to pull this off would be appreciated. Thanks!

Answer 1

Well, it is not LinQ, but it is pretty simple with a DataView

string[] commonCols = obj.Common_Columns;
DataView myTableView = new DataView(srcDataTable); 
DataTable srcReducedTable = myTableView.ToTable(false, commonCols); 

MSDN refs