Full outer join, on 2 data tables, with a list of columns

Question

I have 2 data tables, which I do not know their list of data columns. This list must be extracted at run time, and be used for the full outer join.

When using these

Answer 1

Based on Matthew's answer, I've created a function that accepts more than 2 datatables. I hope it helps:

Usage:

var table123 = FullOuterJoinDataTables(table1, table2, table3);

Here is the function source:

public DataTable FullOuterJoinDataTables(params DataTable[] datatables) // supports as many datatables as you need.
{
    DataTable result = datatables.First().Clone();

    var commonColumns = result.Columns.OfType();

    foreach (var dt in datatables.Skip(1))
    {
        commonColumns = commonColumns.Intersect(dt.Columns.OfType(), new DataColumnComparer());
    }

    result.PrimaryKey = commonColumns.ToArray();

    foreach (var dt in datatables)
    {
        result.Merge(dt, false, MissingSchemaAction.AddWithKey);
    }

    return result;
}

/* also create this class */
public class DataColumnComparer : IEqualityComparer
{
    public bool Equals(DataColumn x, DataColumn y) => x.Caption == y.Caption;       

    public int GetHashCode(DataColumn obj) => obj.Caption.GetHashCode();        
}