How to change DataTable columns order

This is based off of "default locale"'s answer but it will remove invalid column names prior to setting ordinal. This is because if you accidentally send an invalid column name then it would fail and if you put a check to prevent it from failing then the index would be wrong since it would skip indices wherever an invalid column name was passed in.

public static class DataTableExtensions
{
    /// <summary>
    /// SetOrdinal of DataTable columns based on the index of the columnNames array. Removes invalid column names first.
    /// </summary>
    /// <param name="table"></param>
    /// <param name="columnNames"></param>
    /// <remarks> http://stackoverflow.com/questions/3757997/how-to-change-datatable-colums-order</remarks>
    public static void SetColumnsOrder(this DataTable dtbl, params String[] columnNames)
    {
        List<string> listColNames = columnNames.ToList();

        //Remove invalid column names.
        foreach (string colName in columnNames)
        {
            if (!dtbl.Columns.Contains(colName))
            {
                listColNames.Remove(colName);
            }
        }

        foreach (string colName in listColNames)
        {
            dtbl.Columns[colName].SetOrdinal(listColNames.IndexOf(colName));
        }
}

If you have more than 2-3 columns, SetOrdinal is not the way to go. A DataView's ToTable method accepts a parameter array of column names. Order your columns there:

DataView dataView = dataTable.DefaultView;
dataTable = dataView.ToTable(true, "Qty", "Unit", "Id");

Change DataTable Column Order

Input: DataTable Column Order

Columns

1. COLUMN1
2. COLUMN2
3. COLUMN3

You need to Pass DataTable to below method and set the order according to your wish

private void ProcessDataTable(DataTable dt)
{
        //Setting Column Orders
        dt.Columns["COLUMN3"].SetOrdinal(0);
        dt.Columns["COLUMN2"].SetOrdinal(1);
        dt.Columns["COLUMN1"].SetOrdinal(2);
}

Output: DataTable Column Order

Columns

1. COLUMN3
2. COLUMN2
3. COLUMN1

Re-Ordering data Table based on some condition or check box checked. PFB :-

 var tableResult= $('#exampleTable').DataTable();

    var $tr = $(this).closest('tr');
    if ($("#chkBoxId").prop("checked")) 
                    {
                        // re-draw table shorting based on condition
                        tableResult.row($tr).invalidate().order([colindx, 'asc']).draw();
                    }
                    else {
                        tableResult.row($tr).invalidate().order([colindx, "asc"]).draw();
                    }