I want to move the data from a dataColumn to a specific column in my dataTable. I am not sure how to specify what column within my Datatable I want to add the datacolumn.
foreach (DataColumn col in dt.Columns)
{
dt1.Columns.Add(col);
}
I receive an exception Column 'X' already belongs to another DataTable.
You need to copy the properties like ColumnName and create new DataColumns:
foreach (DataColumn col in dt.Columns)
{
dt1.Columns.Add(col.ColumnName, col.DataType);
}
There's a reason for the ArgumentException when you add a DataColumn which already belongs to another DataTable. It would be very dangerous to allow that since a DataTable holds a reference to their columns and every column holds a reference to it's DataTable. If you would add a column to another table your code would blow sooner or later.
If you also want to copy the DataRows into the new table:
foreach (DataRow row in t1.Rows)
{
var r = t2.Rows.Add();
foreach (DataColumn col in t2.Columns)
{
r[col.ColumnName] = row[col.ColumnName];
}
}
You cannot add a DataColumn from another table, because it already has an association with it's original table and a DataColumn is passed by reference to the Add method because it's an Object. You'll have to copy it. Here's one way you can do that:
public static class DataColumnExtensions
{
public static DataColumn CopyTo(this DataColumn column, DataTable table)
{
DataColumn newColumn = new DataColumn(column.ColumnName, column.DataType, column.Expression, column.ColumnMapping);
newColumn.AllowDBNull = column.AllowDBNull;
newColumn.AutoIncrement = column.AutoIncrement;
newColumn.AutoIncrementSeed = column.AutoIncrementSeed;
newColumn.AutoIncrementStep = column.AutoIncrementStep;
newColumn.Caption = column.Caption;
newColumn.DateTimeMode = column.DateTimeMode;
newColumn.DefaultValue = column.DefaultValue;
newColumn.MaxLength = column.MaxLength;
newColumn.ReadOnly = column.ReadOnly;
newColumn.Unique = column.Unique;
table.Columns.Add(newColumn);
return newColumn;
}
public static DataColumn CopyColumnTo(this DataTable sourceTable, string columnName, DataTable destinationTable)
{
if (sourceTable.Columns.Contains(columnName))
{
return sourceTable.Columns[columnName].CopyTo(destinationTable);
}
else
{
throw new ArgumentException("The specified column does not exist", "columnName");
}
}
}
public class MyClass
{
public static void Main()
{
DataTable tableA = new DataTable("TableA");
tableA.Columns.Add("Column1", typeof(int));
tableA.Columns.Add("Column2", typeof(string));
DataTable tableB = new DataTable("TableB");
foreach (DataColumn column in tableA.Columns)
{
column.CopyTo(tableB);
}
}
}
Note that there is also an extension method that can be used to Copy individual columns by name, i.e. tableA.CopyColumnTo("Column1", tableB);.
Then you can copy the data like this if the new table is an exact copy of the original:
foreach (DataRow row in tableA.Rows)
{
tableB.Rows.Add(row.ItemArray);
}
Or in a way similar to the second piece of code in Tim Schmelter's answer if it is not an exact copy. I would, however, recommend some error checking if you aren't copying all the columns into the new table:
foreach (DataRow souceRow in sourceTable.Rows)
{
DataRow destinationRow = destinationTable.Rows.Add();
foreach (DataColumn destinationColumn in destinationTable.Columns)
{
string columnName = destinationColumn.ColumnName;
if (sourceTable.Columns.Contains(columnName))
{
destinationRow[columnName] = sourceRow[columnName];
}
}
}
this is a normal behavior, if you're adding the same column to more than one DataTable ArgumentException will be thrown.
see documentation here:
http://msdn.microsoft.com/en-us/library/55b10992.aspx
you can create a new column same as the one you already added to the original table and add it to the new table.
Table data is organized by row, then by column. You can't (that I know of) add a column of data in one shot. You will need to add the column definition to the second table and add the data to it separately.
Since your original code looped through all columns, you may be better off copying the original datatable using DataTable.Copy() and deleting what you don't want.
Related
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.
The problem: inserting rows only if primary key is bigger than existing one when merging source DataTable to actual DataTable (ActualDT.Merge(SourceDT)).
Details of my problem below:
I fill an Actual DataTable with an Int64 primary key by the API from external server after deserializing JSON to Source DataTable. Then I write rows from DataTable to my database and cleanup all rows in DataTable except the biggest primary key. Later I request new data from the API and often the response contains the same rows I already wrote to database and cleanup from my DataTable.
If I won't cleanup the DataTable rows, performance decrease and it's memory pig. So, I leave one row with the biggest primary key after cleaning.
I don't want to compare every PrimaryKey from Source DataTable before merge, comparing can take a lot of time.
What should I do to prevent merging rows that I already wrote to database and removed from Actual DataTable? Maybe I can exclude them even at deserialisation process (I use NewtonSoft JSON.net)? Or any zippy way to prevent merging rows if they primary key < primary key in Actual DataTable?
Thanks for your answers!
UPDATE: merging code
public class MyData
{
DataTable BlackPairs = new DataTable();
DataTable WhiteTable = new DataTable();
public string _Json {
set
{
DataSet TempDS = JsonConvert.DeserializeObject<DataSet>(value);
try
{
foreach (DataTable table in TempDS.Tables)
{
BlackPairs = table.Copy();
WhiteTable.Merge(BlackPairs);
}
}catch{}
}
}
public MyData()
{ //columns initialization
WhiteTable.Columns.AddRange(new DataColumn[]{columns);
WhiteTable.PrimaryKey = new DataColumn[]{tid};
}
I have created custom Merge function based on what we have talked through comments. This function is only if primary column is typeof(int) but it can be easily improved to get all types or just change it to what type you need (string, int, bool...)
public Test()
{
InitializeComponent();
DataTable smallerDatatable = new DataTable();
smallerDatatable.Columns.Add("Col1", typeof(int));
smallerDatatable.Columns.Add("Col2", typeof(string));
DataTable biggerDatatable = new DataTable();
biggerDatatable.Columns.Add("Col1", typeof(int));
biggerDatatable.Columns.Add("Col2", typeof(string));
smallerDatatable.Rows.Add(1, "Row1");
smallerDatatable.Rows.Add(2, "Row2");
smallerDatatable.Rows.Add(3, "Row3");
biggerDatatable.Rows.Add(1, "Row1");
biggerDatatable.Rows.Add(2, "Row2");
biggerDatatable.Rows.Add(3, "Row3");
biggerDatatable.Rows.Add(4, "Row4");
biggerDatatable.Rows.Add(5, "Row5");
DataTable mergedTable = MergeOnUniqueColumn(smallerDatatable, biggerDatatable, "Col1");
dataGridView1.DataSource = mergedTable;
}
private DataTable MergeOnUniqueColumn(DataTable smallTable, DataTable bigTable, string uniqueColumn)
{
DataTable m = smallTable;
for(int i = 0; i < bigTable.Rows.Count; i++)
{
if(!(smallTable.AsEnumerable().Any(row => bigTable.Rows[i][uniqueColumn].Equals(row.Field<object>(uniqueColumn)))))
{
smallTable.Rows.Add(bigTable.Rows[i].ItemArray);
}
}
return m;
}
Function above will fill every missing unique value inside smallTable from bigTable.
If you want to fill smallTable with values from bigTable only after last smallTable row then use this function.
private DataTable MergeOnUniqueColumnAfterLastID(DataTable smallTable, DataTable bigTable, string uniqueColumn)
{
DataTable m = smallTable;
int maxUnique = Convert.ToInt32(m.Compute("max([" + uniqueColumn + "])", string.Empty));
for (int i = 0; i < bigTable.Rows.Count; i++)
{
if (!(smallTable.AsEnumerable().Any(row => (int)bigTable.Rows[i][uniqueColumn] <= maxUnique)))
{
smallTable.Rows.Add(bigTable.Rows[i].ItemArray);
}
}
return m;
}
Im new to DataSets and I am trying to get a specific column from a DataSet. I wrote this code
using (var dataset = new U2ZFDataSetTableAdapters.stationenTableAdapter())
{
var ds = new U2ZFDataSet();
dataset.Fill(ds.stationen);
var rows = ds.stationen.Select("pdvorhanden = 1");
foreach (DataRow row in rows)
{
foreach (DataColumn column in ds.stationen.Columns)
{
if(column.ColumnName == "Bezeichnung")
listOfStations.Add(row[column].ToString());
}
}
}
The code feels slow to me. Isnt there a better way to do this? How can I get a specific Colum from DataRow without iterating through every column of the row?
Access to the column via column name.
foreach (DataRow row in rows)
{
listOfStations.Add(row["Bezeichnung"].ToString());
}
https://msdn.microsoft.com/en-us/library/146h6tk5(v=vs.110).aspx
So I have a DataTable which uses a "SELECT * FROM People WHERE ID = ?" you can understand that this will only retrieve one row as the ID is unique
I have casted it to a list:
List<DataTable> userInfo = (List<DataTable>)HttpContext.Current.Session["userDT"];
Now I am trying to do a foreach loop that would loop through each row and store the column into a session, this is what I have so far:
However I get an error:
Cannot convert type 'System.Data.DataTable' to 'System.Data.DataRow'
Does anyone know what I am doing wrong?
userInfo is a list of tables. You have to iterate through it, and for each table you can access that table's rows:
foreach (DataTable dt in userInfo)
{
foreach (DataColumn column in dt.Columns)
{
// if you want column names here is how you would get them
string columnName = column.ColumnName;
foreach (DataRow row in dt.Rows)
{
// if you want the values in the cells, here's where you get them
object value = row[column];
}
}
}
Is there anyway to store row header information in a datatable so that when i bind it to a datagridview, it will automatically display both the column and row headers in c#?
Linqpad Demo-Program
As far as i understood you would like to add the column name as values into the datatable / the datagridview. The following is a Linqpad-Program you can easily copy paste into Linqpad to play around. The code adds the column-names to the first row to the datatable. You can easily bind this datatable to a gridview - but beware that each column of the datatable must be of type string.
void Main()
{
GetDataTable().Dump();
}
public DataTable GetDataTable()
{
var dt = new DataTable();
dt.Columns.Add("Id", typeof(string)); // dt.Columns.Add("Id", typeof(int));
dt.Columns["Id"].Caption ="my id";
dt.Columns.Add("Name", typeof(string));
dt.Columns.Add("Job", typeof(string));
dt.Rows.Add(GetHeaders(dt));
dt.Rows.Add(1, "Janeway", "Captain");
dt.Rows.Add(2, "Seven Of Nine", "nobody knows");
dt.Rows.Add(3, "Doctor", "Medical Officer");
return dt;
}
public DataRow GetHeaders(DataTable dt)
{
DataRow dataRow = dt.NewRow();
string[] columnNames = dt.Columns.Cast<DataColumn>()
.Select(x => x.ColumnName)
.ToArray();
columnNames.Dump();
dataRow.ItemArray = columnNames;
return dataRow;
}
Update 2019-06 with additional explanation and alternative code
The method GetHeaders is not the simplest option to get the headers.
Previoulsy the extension method Cast<TResult>(IEnumerable) was used on the DataColumnCollection-Class An alternative would be to just iterate over the collection - this what is done In GetHeadersNew T
public DataRow GetHeadersNew(DataTable dt)
{
DataRow row = dt.NewRow();
DataColumnCollection columns = dt.Columns;
for (int i = 0 ;i <columns.Count ;i++)
{
row[i] = columns[i].ColumnName;
}
return row;
}
This is likely more efficient because less objects and methods are involved.
As long as you can create them with the code based on the data in the row I would just add them at run time using c#. Add a column to the datatable and run through it with a foreach loop. As long as there are not too many rows this code will execute very quickly:
DataTable dt = new DataTable();
// code here to get your datatable
dt.Columns.Add("rowheader");
foreach (DataRow r in dt.Rows)
{
r["rowheader"] = "my nice row header";
}
Then output the new column rowheader as the first cell in the grid.
Another solution is to use the sql query to return an 'extra' column in the result set. for example:
Select *, 'my nice row header' as rowheader from myTable
In this way you make SQL do all the work.