Question

My Table1 has some Header and Values:

KundeID KundeName  Produkt   Comment

1       Michael    Jogurt   "nichts"  
2       Raj                 "Ich bin cool"     
3       Gary       Fanta    "yahoo"  
4       Miky       Sprite  

I want to change to Table2, make Values from Produkt as Header Columns:

KundeID KundeName Comment        Jogurt Fanta Sprite    

1       Michael   "nichts"         x
2       Raj       "Ich bin cool"           
3       Gary      "yahoo"                 x     
4       Miky                                     x         

My code for Table1:

DataTable table = new DataTable("Kunde");

        table.Columns.Add("KundeID", typeof(Int32));
        table.Columns.Add("KundeName", typeof(String));
        table.Columns.Add("Produkt", typeof(String));

        DataTable comment = new DataTable("Comment"); 

        comment.Columns.Add("KundeName", typeof(String));
        comment.Columns.Add("Comment", typeof(String));

        DataSet ds = new DataSet("DataSet");

        ds.Tables.Add(table);
        ds.Tables.Add(comment);

        object[] o1 = { 1, "Michael", "Jogurt" };
        object[] o2 = { 2, "Raj" };
        object[] o3 = { 3, "Gary", "Fanta" };
        object[] o4 = { 4, "Miky", "Sprite" };

        object[] c1 = { "Raj", "Ich bin cool" };
        object[] c2 = { "Gary", "yahoo" };
        object[] c3 = { "Michael", "nichts" };

        table.Rows.Add(o1);
        table.Rows.Add(o2);
        table.Rows.Add(o3);
        table.Rows.Add(o4);

        comment.Rows.Add(c1);
        comment.Rows.Add(c2);
        comment.Rows.Add(c3);

        var results = from table1 in table.AsEnumerable()
                      join table2 in comment.AsEnumerable()
                      on table1.Field<string>("KundeName") equals table2.Field<string>("KundeName") into prodGroup
                      from table4 in prodGroup.DefaultIfEmpty()

                      select new
                          {
                              KundeID = table1.Field<Int32?>("KundeID"),
                              KundeName = table1.Field<String>("KundeName"),
                              Produkt = table1.Field<String>("Produkt"),
                              Comment = table4 != null ? table4.Field<String>("Comment") : null,
                          };
dataGridView1.DataSource = results.ToList();

How can I take Value from “Produkt” and make it Header? thank you guys for helping

Answer 1

This should do the trick regardless of how many different products come up. It’s pretty short and concise.

// build the new data table
var result = new DataTable();
result.Columns.Add("KundeID", typeof(Int32));
result.Columns.Add("KundeName", typeof(String));
result.Columns.Add("Comment", typeof(String));
result.Columns.AddRange(
    (from c in 
         (from r in table.AsEnumerable() 
          where !r.IsNull("Produkt") && !string.IsNullOrEmpty(r.Field<string>("Produkt")) 
          select r.Field<string>("Produkt")).Distinct()    // added DISTINCT
     select new DataColumn(c, typeof(bool))).ToArray()
);

foreach (var r in results)
{
    var productIndex = result.Columns.IndexOf(r.Produkt);
    var vals = new List<object>() { r.KundeID, r.KundeName, r.Comment };
    for (int i = 3; i < result.Columns.Count; i++)
    {
        if (i == productIndex)
        {
            vals.Add(true);
        }
        else
        {
            vals.Add(false);
        }
    }

    result.LoadDataRow(vals.ToArray(), true);
}