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How to copy only required rows of old DataTable to the new DataTable rows having different structure?

I have a requirement where I need to copy the existing DataTable rows/values to the new DataTable,
New DataTable is of custom(different column names) structure/schema as we need this new DataTable data to be exported to Excel file later.
To copy the required column values to the new DataTable I have created string Array which contains required column names(columns from which we need to copy data to new DataTable) of existing DataTable, given below.
string[] selectedColumns = new[] { "SUPPLIER_NAME", "SUPPLIER_NO", "CONFIRMATION_NO", "RELEASE_NO", "WCO_INVOICE_NO",
"CUSTOMER_BILLED", "BALANCE_TOBILL", "SUPP_INVOICE_NO", "SUPPLIER_PAID", "BALANCE_COST" }; //TODO Add columns "WCO_INVOICE_DATE", "SUPPLIER_INVOICE_DATE" later.
For getting the required DataTable, I have created a method which will be called like below by passing existing DataTable and selected columns of existing DataTable column names as an parameters.
DataTable _dtPrjLedgerExportData = ControllerClass.dtProjectLedgerExport(dtfilter, selectedColumns);
ControllerClass Class dtProjectLedgerExport method will return the newly created DataTable i.e. DataTable with the customize Column names and the values pulled from existing DatTable,
New DataTable additionally contain two new columns (WCO_Invoice_Date, Supplier_Invoice_Date) with default blank values (set from the code).
public static DataTable dtProjectLedgerExport(DataTable dtToExport, string[] selectedColumns)
{
DataTable dt = new DataTable();
dt.Columns.Add("Supplier");
dt.Columns.Add("Supplier_No");
dt.Columns.Add("Confirmation_Number");
dt.Columns.Add("Release_Number");
dt.Columns.Add("WCO_Invoice_No");
dt.Columns.Add("WCO_Invoice_Date");
dt.Columns.Add("Customer_Billed_Amt");
dt.Columns.Add("Balance_Remaining_to_Bill");
dt.Columns.Add("Supplier_Invoice_Number");
dt.Columns.Add("Supplier_Invoice_Date");
dt.Columns.Add("Supplier_Paid_Amt");
dt.Columns.Add("Remaining_Cost_Dollar_Balance");
//temporarily set default value for non-existing rows
dt.Columns["WCO_Invoice_Date"].DefaultValue = string.Empty;
dt.Columns["Supplier_Invoice_Date"].DefaultValue = string.Empty;
//Copy rows to dt
if (dtToExport != null && dtToExport.Rows.Count > 0)
dt = new DataView(dtToExport).ToTable(false, selectedColumns);
return dt;
}
Problem:
The above code is not working as expected it is returning Data of existing DataTable with the same structure.
What changes are required in above code to get the expected result?

I'd use this approach:
public static DataTable DtProjectLedgerExport(DataTable dtToExport, string[] selectedColumns, params string[] additionalColumns)
{
DataTable dt = dtToExport.Copy(); // add columns and data
List<DataColumn> removeColumns = dt.Columns.Cast<DataColumn>()
.Where(c => !selectedColumns.Contains(c.ColumnName, StringComparer.InvariantCultureIgnoreCase))
.ToList();
removeColumns.ForEach(dt.Columns.Remove);
foreach (string colName in additionalColumns)
{
DataColumn newColumn = new DataColumn(colName);
newColumn.DefaultValue = string.Empty;
dt.Columns.Add(newColumn);
}
return dt;
}

After stating in the comments that you have different column names in each table...(Seriously that's a critical piece of information lol)! The only way is to basiaclly map the values yourself for each column like so.
public static DataTable dtProjectLedgerExport(DataTable dtToExport)
{
DataTable dt = new DataTable();
dt.Columns.Add("Supplier");
dt.Columns.Add("Supplier_No");
dt.Columns.Add("Confirmation_Number");
dt.Columns.Add("Release_Number");
dt.Columns.Add("WCO_Invoice_No");
dt.Columns.Add("WCO_Invoice_Date");
dt.Columns.Add("Customer_Billed_Amt");
dt.Columns.Add("Balance_Remaining_to_Bill");
dt.Columns.Add("Supplier_Invoice_Number");
dt.Columns.Add("Supplier_Invoice_Date");
dt.Columns.Add("Supplier_Paid_Amt");
dt.Columns.Add("Remaining_Cost_Dollar_Balance");
foreach (var expRow in dtToExport.Rows)
{
var row = dt.NewRow();
row["Supplier"] = expRow["Supplier_Name"];
//repeat for all columns you want.
dt.Rows.Add(row);
}
return dt;
}

Well, of course, because you finally override dt completely. You should enumerate the rows in dtToExport in a loop and create new rows in dt and assign the values for every field you need.

Datatable values to datagridview, only showing one columns data

I have a datatable filled with a report from a web service. I am now trying to display the datatable in an datagridview. This is the code I use to build the datatable:
// Create DataTabe to handle the output
DataTable dt = new DataTable();
dt.Clear();
dt.Columns.Add("EmployeeFirstName");
dt.Columns.Add("EmployeeLastName");
dt.Columns.Add("DepartmentName");
dt.Columns.Add("DepartmentCode");
dt.Columns.Add("LocationName");
dt.Columns.Add("DivisionCode");
dt.Columns.Add("EarningName");
dt.Columns.Add("OTHours");
dt.Columns.Add("WorkDate")
Fill the new datatable:
foreach (ReportRow row in report.Rows)
{
dt.Rows.Add(string.Join(",", row.ColumnValues));
}
Then I try to bind the data in the datatable to the dataGridview:
dataGridView1.AutoGenerateColumns = true;
dataGridView1.DataSource = dt;
dataGridView1.Refresh();
When I run the application it only displays the data from the first column in the datatable. Do I need a loop of sorts to work through the columns or am I just missing a step?

Yes that's cause you are adding only one value to your dt when you say dt.Rows.Add(string.Join(",", row.ColumnValues));. You should be doing something like below (assuming that ReportRow also has the columns with same names like "EmployeeFirstName" else change the names accordingly)
foreach (ReportRow row in report.Rows)
{
DataRow dr = dt.NewRow();
dr["EmployeeFirstName"] = row["EmployeeFirstName"];
dr["EmployeeLastName"] = row["EmployeeLastName"];
dr["DepartmentName"] = row["DepartmentName"];
//rest of the columns fill
//once all columns filled
dt.Rows.Add(dr);
}

dt.Rows.Add(string.Join(",", row.ColumnValues)); -> You can either add a single DataRow item or a array of objects.
From your call, you chose the later, you are adding a array of objects, except you are adding ONE SINGLE object.
string.Join(",", row.ColumnValues) is one object.

Well after sleeping I have found the issue with dropping it into an sql table... I didn't take into account that the export to a CSV and the addition of the " , " would affect the export to sql. Here is the modification of the lines of code that was the issue:
foreach (ReportRow row in report.Rows)
{
dt.Rows.Add(row.ColumnValues);
}
Thank you all for your responses!

Copy one datatable to another datatable in asp.net

I have created a datatable which has some records, now what I want is to copy the record of first datatable to another datatable.
I tried like below:
Session["AmountData"] = AmountDatatable; // 1st datatable which has data
DataTable CompanyWiseRecord = new DataTable();
for (int i = 0; i < AmountDatatable.Rows.Count; i++)
{
CompanyWiseRecord.ImportRow(AmountDatatable.Rows[i]); // 2nd datatable which does not have data
}
Kindly let me know where I am going wrong.

You directly use session Like:
DataTable CompanyWiseRecord = (DataTable)Session["AmountData"]; //Retrieving DataTable from Session.

if you are not fetching data from table one based on some condition or assign particular rows or columns then You can do it simply by using
DataTable CompanyWiseRecord=AmountDatatable;

Adding a column from one Datatable to another datatable of a dataset [duplicate]

How can I copy 1 data column from 1 data table to a new datatable. When I try to do it, I get the error Column 'XXX' already belongs to another DataTable.?
dataColumn = datatable1.Columns[1];
datatable2 = new DataTable();
datatable2.Columns.Add(dataColumn);
Thanks in Advance

You cannot copy DataColumns. What you'll need to do is create a new DataColumn in the new datatable with the same data type as in the old datatable's column, and then you need to run a FOR loop to bring in all the data from the old datatable to the new datatable.
See the following code. This assumes that the datatables have exactly the same number of rows.
DataTable dt1 = new DataTable();
DataTable dt2 = new DataTable();
dt2.Columns.Add("ColumnA", dt1.Columns["ColumnA"].DataType);
for (int i = 0; i < dt1.Rows.Count; i++)
{
dt2.Rows[i]["ColumnA"] = dt1.Rows[i]["ColumnA"];
}
Also, If the data you are copying are reference types and not value types you might want to see if a .Clone() method is available for the type, or make one yourself. Just doing 'this = that' in the FOR loop will not work on reference types.

You cannot copy a DataColumn. (DataColumns are very tightly coupled with their tables)
Instead, you can add a new column with the same name and datatype.
You might be looking for DataTable.Clone(), which will create a structual copy of an entire table. (With the same schema, but no data)

Just a thought, are your DataTables both in the same DataSet?
If so, you can create a named DataRelation between the columns of two tables (think foreign key).
Then you can add a Calculated DataColumn to your table that has its Expression property set to "Child(RelationName).ColumnName" or "Parent(RelationName).ColumnName" depending on the direction of the relationship.
This will give you the same effect as copying the column, but I believe it only evaluates it lazily. So maybe it will give you what you need.
There is an example here of how this works. The example uses the Sum aggregate function, but you just need to reference the column name and it will duplicate it in your DataTable
myDataSet.Relations.Add(
"Orders2OrderLines",
myDataSet.Tables["Orders"].Columns["OrderID"],
myDataSet.Tables["OrderLines"].Columns["OrderID"]);
ordersTable.Columns.Add("OrderTotal", typeof(decimal), "Sum(Child(Orders2OrderLines).ExtendedPrice)");
HTH

The problem is caused by the c# can not reuse the object instance created and uses it on multiples DataTables. For this it is necessary to create a new object DataCollumn for each loop iteration.
foreach (DataTable table in DATASET.Tables)
{
DataColumn yourDataCollumn = new DataColumn("Name of DataCollumn", typeof(Your data type));
// your logic here
}
Hope it's help...

I used the below to merge two tables using mostly LINQ and only looping through the rows at the end. I wouldn't call it pretty but it does work. Using the join to prevent some of the assumptions listed above.
DataTable tableOne = getTableOne();
DataTable tableTwo = getTableTwo();
var oneColumns = tableOne.Columns.Cast<DataColumn>()
.Select(p => new Column(p.ColumnName, DataType))
.ToArray();
var twoColumns = tableTwo.Columns.Cast<DataColumn>()
.Select(p => new DataColumn(p.ColumnName, p.DataType))
.ToArray();
var matches = (from a in tableOne.AsEnumerable()
join b in tableTwo.AsEnumerable() on a["column_name"] equals b["column_name"]
select a.ItemArray.Concat(b.ItemArray)).ToArray();
DataTable merged = new DataTable();
merged.Columns.AddRange(oneColumns);
merged.Columns.AddRange(twoColumns);
foreach (var m in matches) { merged.Rows.Add(m.ToArray()); }

No looping required , Refer this , Hope this should solve your problem...
DataTable dt = new DataTable();
//fill the dt here
DataTable dt2 = new DataTable();
string[] strCols = {"Column Name to copy"};
dt2 = dt.DefaultView.ToTable("newTableName", false, strCols);

Copy DataTable from one DataSet to another

I'm trying to add to a new DataSet X a DataTable that is inside of a different DataSet Y.
If I add it directly, I get the following error:
DataTable already belongs to another DataSet.
Do I have to clone the DataTable and import all the rows to it and then add the new DataTable to the new DataSet? Is there a better/easy way to do it?

There are two easy ways to do this:
DataTable.Copy
Instead of DataTable.Clone, use DataTable.Copy to create a copy of your data table; then insert the copy into the target DataSet:
dataSetX.Tables.Add( dataTableFromDataSetY.Copy() );
DataSet.Merge
You could also use DataSet.Merge for this:
dataSetX.Merge(dataTableFromDataSetY);
Note, however, that if you are going to use this method, you might want to make sure that your target DataSet doesn't already contain a table with the same name:
If the target DataSet doesn't contain a table by the same name, a fresh copy of the table is created inside the data set;
If a table by the same name is already in the target data set, then it will get merged with the one passed to Merge, and you end up with a mix of the two.

Use this generic function
public DataTable CopyDataTable(DataTable dtSource, int iRowsNeeded)
{
if (dtSource.Rows.Count > iRowsNeeded)
{
// cloned to get the structure of source
DataTable dtDestination = dtSource.Clone();
for (int i = 0; i < iRowsNeeded; i++)
{
dtDestination.ImportRow(dtSource.Rows[i]);
}
return dtDestination;
}
else
return dtSource;
}
Suppose you want to copy first table of sourceSet to destinationSet.
Call it like
DataTable destinationTable = CopyDataTable(sourceSet.Tables[0], sourceSet.Tables[0].Rows.Count);
DataSet destinationSet = new DataSet();
destinationSet.Tables.Add(destinationTable);

This should work for you
X.Tables.Add(Y.Tables[<tablename|index>].Copy());

IEnumerable<DataRow> query = from sourceTbl in sourceTbl.AsEnumerable()
where [any condition you want]
select order;
DataTable boundTable = query.CopyToDataTable<DataRow>();
I am not sure If i understood your question properly.Hope this code helps