Develop Reference

Copy row from datatable to another where there are common column headers

I have two datatables, I am trying to copy row from one table to another, I have tried this. the thing is that my tables are not exactly the same, both tables have common headers, but to the second table have more columns, therefore I need "smart" copy, i.e to copy the row according to the column header name.
d1:
+--------+--------+--------+
| ID | aaa | bbb |
+--------+--------+--------+
| 23 | value1 | value2 | <----copy this row
d2:
+--------+--------+--------+--------+
| ID | ccc | bbb | aaa |
+--------+--------+--------+--------+
| 23 | | value2 | value1 | <----I need this result
but this code:
string rowID=23;
DataRow[] result = dt1.Select($"ID = {rowID}");
dt2.Rows.Add(result[0].ItemArray);
gives:
d2:
+--------+--------+--------+--------+
| ID | ccc | bbb | aaa |
+--------+--------+--------+--------+
| 23 | value1 | value2 | | <---- :( NOT what I need

I think this is your homework, but here you have some simple and not very smart solution:
private DataTable DTCopySample()
{
int cnt = 0;
DataTable dt1 = new DataTable();
dt1.Columns.Add("ID");
dt1.Columns.Add("aaa");
dt1.Columns.Add("bbb");
DataTable dt2 = new DataTable();
dt2.Columns.Add("ID");
dt2.Columns.Add("ccc");
dt2.Columns.Add("bbb");
dt2.Columns.Add("aaa");
dt1.Rows.Add();
dt1.Rows[0]["ID"] = "23";
dt1.Rows[0]["aaa"] = "val1";
dt1.Rows[0]["bbb"] = "val2";
dt1.Rows.Add();
dt1.Rows[1]["ID"] = "99";
dt1.Rows[1]["aaa"] = "val99";
dt1.Rows[1]["bbb"] = "val98";
string colName = string.Empty;
foreach (DataRow row in dt1.Rows)
{
dt2.Rows.Add();
foreach (DataColumn col in dt1.Columns)
{
dt2.Rows[cnt][col.ColumnName] = row[col.ColumnName].ToString();
}
cnt++;
}
return dt2;
}
There are more smart and better solutions, but this is fast-written (2 mins) and works.
Remeber, that you have not specified columns datatypes or anything else, so I assumed there are strings everywhere for creating simple sample.

linq Group By from DataTable

I have DataTable Like this
Thank you Bob Vale for your help
what is (Select(X,i) mean in your linq,
but as i made a mistake in my table
I have this
No | Size | Type | FB | FP
----------------------------------------
100 | 2 | typeA | FB1 | A1
101 | 3 | typeB | FB1 | A1
101 | 4 | typec | FB1 | A1
103 | 4 | typeC | FB2 | A2
103 | 5 | typeD | FB2 | A2
103 | 6 | typeE | FB2 | A2
I want to have some thing like that
No | Size | Type | FB | FP
---------------------------------
100 | 2 | typeA | FB1 | A1
101 | 3 | typeB | FB1 | A1
| 4 | typec | |
103 | 4 | typeC | FB2 | A2
| 5 | typeD | |
| 6 | typeE | |
How can I make it? I can make Group By
var result = from row in cableDataTable.AsEnumerable()
group row by new
{
FB = row.Field<string>("FB"),
FP = row.Field<string>("FP"),
Size = row.Field<int>("Size"),
Type = row.Field<int>("Type"),
no= row.Field<int>("no"),
} into g
select new
{
FB = g.Key.FB,
FP = g.Key.FP,
Size = g.Key.Size,
Type = g.Key.Type
no= g.Key.no
};
but it that could't give the result
thank you for your attention

How about this:
// First declare a conversion from the DataTable to an anon type
var rows = cableDataTable.AsEnumerable()
.Select(x => new {
Size = x.Field<int>("Size"),
Type= x.Field<string>("Type"),
FB = x.Field<string>("FB"),
FP = x.Field<string>("FP")
});
// Now use group by, ordering and select many to select the rows
var result = rows.GroupBy (row => new {row.FB, row.FP} )
.OrderBy (g => g.Key.FB)
.ThenBy(g => g.Key.FP)
.SelectMany(g => g.OrderBy(row => row.Size)
.Select((x,i) =>
new {
Size = x.Size,
Type = x.Type,
FB = (i==0) ? x.FB : null,
FP= (i==0) ? x.FP : null
}));

You can use linq query as
var result = cableDataTable.AsEnumerable().GroupBy(g => new { g.FB, g.FP}).Select(x => x);

Check occurrence of word appearing in datatable column

I have the data below in a datatable this is example data. I would like get the occurrence of 12,13 in the datatable as normally there would be 10-20 million row in the datatable.
Customer | quantity | Product | Code
1 | 3 | Product | 12
2 | 4 | Product | 13
3 | 1 | Product | 12
4 | 6 | Product | 13

how about simple for each loop
private int getCount(int yourSearchDigit)
{
int counter = 0;
foreach (DataRow dr in youDataTable.Rows)
{
if (Convert.ToInt32(dr["Code"]) == yourSearchDigit)
counter++;
}
return counter;
}

You can use Linq-To-DataTable:
int[] allowedCodes = new []{ 12, 13 };
var rows = table.AsEnumerable()
.Where(r => allowedCodes.Contains(r.Field<int>("Code")));
However, if you have 10-20 million row in the datatable you should consider to do the filtering in the database itself.
If you want to know the number they occur:
int count = table.AsEnumerable()
.Count(r => allowedCodes.Contains(r.Field<int>("Code")));

How to select rows from DataTable based on Index / Row Number?

I have a DataTable. I want to select the rows based on the Index/Row Number of the rows in DataTable.
Suppose below is the DataTable:
---------------- ---------------
| ID | Name | | Index/RowNo |
---------------- ---------------
| A001 | John | | 1 |
| A002 | Foo | | 2 |
| A003 | Rambo | | 3 |
| A004 | Andy | | 4 |
| ... | ... | | 5 |
---------------- ---------------
Now, i want to select the Rows from above shown DataTable using criteria say for example Index > 2, In that case First entry at Index 1, A001 | John, will not become part of the resultant DataTable. How can i do it efficiently?
Moreover, i want to have my result both in the form of DataTable and Linq query outcome.
I am trying to do something like this:
var result = dt.Select("RowNum > 1", "");
OR
var result = from row in dt.AsEnumerable()
where RowNum > 1
select row;

I am trying to do something like this:
var result = dt.Select("RowNum > 1", "");
You can use Enumerable.Skip even with a DataTable since it is an IEnumerable<DataRow>:
IEnumerable<DataRow> allButFirst = table.AsEnumerable().Skip(1);
get a new DataTable with:
DataTable tblAllButFirst = allButFirst.CopyToDataTable();
If your next question is how you can take only rows with given indices:
var allowedIndices = new[]{ 2, 4, 7, 8, 9, 10 };
DataTable tblAllowedRows = table.AsEnumerable()
.Where((r, i) => allowedIndices.Contains(i))
.CopyToDataTable();

var result = table.AsEnumerable()
.Where((row, index) => index > 1)
.CopyToDataTable()

Sort several duplicate values in DataTable to one row

I've imported a DataTable from a SQL Database using SqlDataAdapter and Fill-Method.
My datatable looks like this:
Timestamp(unix time) | Value
x | 10
x | 42
x | 643
y | 5
y | 9
y | 70
...and so on. The table contains a lot of values (1000+) but has always three rows with the same timestamp.
Now I want it to look like this:
Timestamp(unix time) | Value 1 | Value 2 | Value 3
x | 10 | 42 | 643
y | 5 | 9 | 70
How can I sort it this way?
(If there are more than three values, the programm should just insert the first three values it has found)
Thanks for any help!

Thanks for your approach! I solved it myself now.
This is how I've done it:
var grouped = from myRow in myDataTable.AsEnumerable()
group myRow by myRow.Field<int>("TIMESTAMP");
foreach (var timestamp in grouped)
{
string[] myRow = new string[5];
myRow[0] = timestamp.Key.ToString();
int i = 1;
foreach (var value in timestamp)
{
myRow[i] = value.Field<double>("VALUE").ToString();
i++;
if (i > 4)
break;
}
mySortedTable.Rows.Add(myRow);
}

I think this may also be solvable in SQL, but if you want to do it programmatically, I have tested the following in LinqPad:
void Main()
{
var list = new List<Tuple<string,int>> {
Tuple.Create("x", 10),
Tuple.Create("x", 42),
Tuple.Create("x", 643),
Tuple.Create("y", 5),
Tuple.Create("y", 9),
Tuple.Create("y", 70),
};
var result =
from grp in list.GroupBy(t => t.Item1)
let firstThree = grp.Select(t => t.Item2).Take(3).ToList()
select new {
Key = grp.Key,
Value1 = firstThree[0],
Value2 = firstThree[1],
Value3 = firstThree[2] };
foreach (var item in result)
Console.WriteLine(item);
}
It assumes that you have at least three elements, otherwise you'll get an out of range exception.
While the end result is an anonymous type, you could easily pipe the results of the operation into a DataRow instead.