How to add identity column to datatable using c#. Im using Sql compact server.
You could try something like this maybe?
private void AddAutoIncrementColumn()
{
DataColumn column = new DataColumn();
column.DataType = System.Type.GetType("System.Int32");
column.AutoIncrement = true;
column.AutoIncrementSeed = 1000;
column.AutoIncrementStep = 10;
// Add the column to a new DataTable.
DataTable table = new DataTable("table");
table.Columns.Add(column);
}
DataTable table = new DataTable("table");
DataColumn dc= table.Columns.Add("id", typeof(int));
dc.AutoIncrement=true;
dc.AutoIncrementSeed = 1;
dc.AutoIncrementStep = 1;
// Add the new column name in DataTable
table.Columns.Add("name",typeof(string));
table.Rows.Add(null, "A");
table.Rows.Add(null, "B");
table.Rows.Add(null, "C");
If the DataTable is already populated. you can use below method
void AddAndPopulateDataTableRowID(DataTable dt, string col, bool isGUID)
{
if(isGUID)
dt.Columns.Add(col, typeof(System.Guid));
else
dt.Columns.Add(col, typeof(System.Int32));
int rowid = 1;
foreach (DataRow dr in dt.Rows)
{
if (isGUID)
dr[col] = Guid.NewGuid();
else
dr[col] = rowid++;
}
}
You don't do autoincrement on DataTable (or front-end for that matter), unless you want to make your application a single user application only.
If you need the autoincrement, just do it in database, then retrieve the autoincremented id produced from database to your front-end.
See my answer here, just change the SqliteDataAdapter to SqlDataAdapter, SqliteConnection to SqlConnection, etc : anyway see why I get this "Concurrency Violation" in these few lines of code??? Concurrency violation: the UpdateCommand affected 0 of the expected 1 records
Just my two cents. Auto-increment is useful in a Winform app (stand alone as Michael Buen rightly said), i.e.:
DatagridView is being used to display data that does not have a "key field", the same can be used for enumeration.
I dont think its a good idea to use autoincrement on datatable if you are using insert and delete to a datatable because the number will not be rearranget, no final i will share a small idea how can we use autoincrement manual.
DataTable dt = new DataTable();
dt.Columns.Add("ID",typeof(int));
dt.Columns.Add("Produto Nome", typeof(string));
dt.Rows.Add(null, "A");
dt.Rows.Add(null, "B");
dt.Rows.Add(null, "C");
for(int i=0;i < dt.Rows.Count;i++)
{
dt.Rows[i]["ID"] = i + 1;
}
always when finalizing the insert or delete must run this loop
for(int i=0;i < dt.Rows.Count;i++)
{
dt.Rows[i]["ID"] = i + 1;
}
Related
I have a DataTable that is populated with only strings at the moment.
I want to get from the DataTable Columns the DataType and insert the DataType.
DataTable example, all row names can be random.
And I want to have from the example Column "age" as int, and the rest still string.
At the moment the Age is a string, can I try to Parse the whole column? Or would this be a bad solution.
Is there a simple way to do this?
You can not change the data type once the table is loaded. Clone the current DataTable from the original table, find the age column, change data type from string to int then import rows.
Important: The above assumes that, in this case the age column can represent an int on each row, if not you need to perform proper assertion before using ImportRow.
Here is a conceptual example
private static void ChangeColumnType()
{
DataTable table = new DataTable();
table.Columns.Add("Seq", typeof(string));
table.Columns.Add("age", typeof(string));
table.Columns.Add("name", typeof(string));
table.Rows.Add("1", "22", "Smith");
table.Rows.Add("2", "46", "Jones");
DataTable cloned = table.Clone();
bool found = false;
for (int index = 0; index < table.Columns.Count; index++)
{
if (string.Equals(table.Columns[index].ColumnName, "age",
StringComparison.CurrentCultureIgnoreCase))
{
cloned.Columns["age"]!.DataType = typeof(int);
found = true;
}
}
if (!found) return;
foreach (DataRow row in table.Rows)
{
cloned.ImportRow(row);
}
foreach (DataColumn column in cloned.Columns)
{
Console.WriteLine($"{column.ColumnName}\t{column.DataType}");
}
}
Edit: One possible way to avoid issues when age can not be converted to an int.
if (!found) return;
foreach (DataRow row in table.Rows)
{
if (int.TryParse(row.Field<string>("age"), out _))
{
cloned.ImportRow(row);
}
else
{
Console.WriteLine($"Failed: {string.Join(",", row.ItemArray)}");
}
}
Sorry if I do not understand your question but I will try to answer what I think you're asking below:
If you're just trying to determine the data type then I would suggest taking the first value in said column (as you don't need to check them all obviously.) And do a tryparse to determine if it is compatible with int for example.
If you used getType it would likely return a String.
If you're trying to SET the whole column as a data type then you should probably be doing this at the stage you're generating the table via a constructor or programatically as shown in the first example
// Create second column.
column = new DataColumn();
column.DataType = System.Type.GetType("System.String");
column.ColumnName = "ParentItem";
column.AutoIncrement = false;
column.Caption = "ParentItem";
column.ReadOnly = false;
column.Unique = false;
// Add the column to the table.
table.Columns.Add(column);
Full Example from Microsoft
Here is my code:
private void AddAutoIncrementColumn(DataTable dt)
{
DataColumn column = new DataColumn();
column.DataType = System.Type.GetType("System.Int32");
column.AutoIncrement = true;
column.AutoIncrementSeed = 0;
column.AutoIncrementStep = 1;
dt.Columns.Add(column);
}
I have an existing DataTable and want to create an auto-incremented column. That is, when i create the column i want it to automatically fill in the value 0......x. I am using the code above. But it doesn't seem to work. Any suggestions?
Try This
private void AddAutoIncrementColumn()
{
DataColumn column = new DataColumn();
column.DataType = System.Type.GetType("System.Int32");
column.AutoIncrement = true;
column.AutoIncrementSeed = 0;
column.AutoIncrementStep = 1;
// Add the column to a new DataTable.
DataTable table = new DataTable("table");
table.Columns.Add(column);
}
There is a method on Datatable called CreateDataReader. So, clone your original datatable, add the identity column, create a datareader from the original table, then load the cloned table with the data reader. This will generate numbers in the identity column in the cloned table, then discard the original table and use the clone, eg
// original data table
DataTable origDT;
// create a reader
DataReader dr = origDT.CreatDataReader();
//clone original
DataTable clonedDT = origDT.Clone();
//add identity column
clonedDT.Columns.Add(new DataColumn(){AutoIncrement=true});
//load clone from reader, identity col will auto-populate with values
clonedDT.Load(dr);
Hi. I have a DataTable one of the column is set to AutoIncrement is true. Basically I am adding some text box values to the DataTable and then binding it to the Grid View. What I am trying to achieve is if I delete a row from the grid view the row in the DataTable is also need to be deleted and also decrement the primary key column.
DataTable is declared like this private DataTable table = new DataTable(); and code is:
DataColumn promoDetailsID = new DataColumn();
promoDetailsID.ColumnName = "promoDetailsID";
promoDetailsID.DataType = System.Type.GetType("System.Int32");
promoDetailsID.AutoIncrement = true;
promoDetailsID.AutoIncrementSeed = 1;
promoDetailsID.AutoIncrementStep = 1;
table.Columns.Add(promoDetailsID);
table.Columns.Add("StartRange", typeof(string));
table.Columns.Add("EndRange", typeof(string));
table.Columns.Add("Amount", typeof(string));
table.Columns.Add("AllocationCases", typeof(string));
table.Columns.Add("AllocationUnits", typeof(string));
if (ViewState["dtTable"] != null)
{
table = (DataTable)ViewState["dtTable"];
}
table.Rows.Add(null,TxtStartRange.Text.Trim(), TxtEndRange.Text.Trim(), TxtAllocationAmount.Text.Trim(), TxtAllocationCases.Text.Trim(), TxtAllocationUnits.Text.Trim());
grdPromotions.DataSource = table;
grdPromotions.DataBind();
ViewState["dtTable"] = table;
This is the code when I am trying to delete row from grid.
protected void grdPromotions_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
if (ViewState["dtTable"] != null)
{
table = (DataTable)ViewState["dtTable"];
int rowIndex = Convert.ToInt32(e.RowIndex);
table.Rows[e.RowIndex].Delete();
}
table.AcceptChanges();
grdPromotions.DataSource = table;
grdPromotions.DataBind();
ViewState["dtTable"] = table;
}
There is no error I am getting but the DataTable is not updating after delete.
Since you don't use a real database it makes no sense to use DataRow.Delete which just sets it's RowState to Deleted. What you want to do is to remove the row from the DataTable.
table.Rows.RemoveAt(e.RowIndex);
If you also want to decrement the primary key column, you have to make the column writable:
table.Columns[0].ReadOnly = false;
Then you need to update the value manually:
int counter = 0;
foreach(DataRow row in table.Rows)
{
row[0] = ++counter;
}
table.Columns[0].ReadOnly = true;
Side-note: don't store a DataTable in ViewState, if you need to persist it between postbacks use the Session instead. Session lives in memory whereas ViewState will be serialized and stored in the rendered html, so it will also be transferred to the client.
We have two columns in a DataTable, like so:
COL1 COL2
Abc 5
Def 8
Ghi 3
We're trying to sort this datatable based on COL2 in decreasing order.
COL1 COL2
ghi 8
abc 4
def 3
jkl 1
We tried this:
ft.DefaultView.Sort = "COL2 desc";
ft = ft.DefaultView.ToTable(true);
but, without using a DataView, we want to sort the DataTable itself, not the DataView.
I'm afraid you can't easily do an in-place sort of a DataTable like it sounds like you want to do.
What you can do is create a new DataTable from a DataView that you create from your original DataTable. Apply whatever sorts and/or filters you want on the DataView and then create a new DataTable from the DataView using the DataView.ToTable method:
DataView dv = ft.DefaultView;
dv.Sort = "occr desc";
DataTable sortedDT = dv.ToTable();
This will help you...
DataTable dt = new DataTable();
dt.DefaultView.Sort = "Column_name desc";
dt = dt.DefaultView.ToTable();
Its Simple Use .Select function.
DataRow[] foundRows=table.Select("Date = '1/31/1979' or OrderID = 2", "CompanyName ASC");
DataTable dt = foundRows.CopyToDataTable();
And it's done......Happy Coding
Maybe the following can help:
DataRow[] dataRows = table.Select().OrderBy(u => u["EmailId"]).ToArray();
Here, you can use other Lambda expression queries too.
Or, if you can use a DataGridView, you could just call Sort(column, direction):
namespace Sorter
{
using System;
using System.ComponentModel;
using System.Windows.Forms;
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
this.dataGridView1.Rows.Add("Abc", 5);
this.dataGridView1.Rows.Add("Def", 8);
this.dataGridView1.Rows.Add("Ghi", 3);
this.dataGridView1.Sort(this.dataGridView1.Columns[1],
ListSortDirection.Ascending);
}
}
}
Which would give you the desired result:
Did you try using the Select(filterExpression, sortOrder) method on DataTable? See here for an example. Note this method will not sort the data table in place, if that is what you are looking for, but it will return a sorted array of rows without using a data view.
table.DefaultView.Sort = "[occr] DESC";
Use LINQ - The beauty of C#
DataTable newDataTable = baseTable.AsEnumerable()
.OrderBy(r=> r.Field<int>("ColumnName"))
.CopyToDataTable();
There is 2 way for sort data
1) sorting just data and fill into grid:
DataGridView datagridview1 = new DataGridView(); // for show data
DataTable dt1 = new DataTable(); // have data
DataTable dt2 = new DataTable(); // temp data table
DataRow[] dra = dt1.Select("", "ID DESC");
if (dra.Length > 0)
dt2 = dra.CopyToDataTable();
datagridview1.DataSource = dt2;
2) sort default view that is like of sort with grid column header:
DataGridView datagridview1 = new DataGridView(); // for show data
DataTable dt1 = new DataTable(); // have data
dt1.DefaultView.Sort = "ID DESC";
datagridview1.DataSource = dt1;
It turns out there is a special case where this can be achieved. The trick is when building the DataTable, collect all the rows in a list, sort them, then add them. This case just came up here.
//Hope This will help you..
DataTable table = new DataTable();
//DataRow[] rowArray = dataTable.Select();
table = dataTable.Clone();
for (int i = dataTable.Rows.Count - 1; i >= 0; i--)
{
table.ImportRow(dataTable.Rows[i]);
}
return table;
TL;DR
use tableObject.Select(queryExpression, sortOrderExpression) to select data in sorted manner
Complete example
Complete working example - can be tested in a console application:
using System;
using System.Data;
namespace A
{
class Program
{
static void Main(string[] args)
{
DataTable table = new DataTable("Orders");
table.Columns.Add("OrderID", typeof(Int32));
table.Columns.Add("OrderQuantity", typeof(Int32));
table.Columns.Add("CompanyName", typeof(string));
table.Columns.Add("Date", typeof(DateTime));
DataRow newRow = table.NewRow();
newRow["OrderID"] = 1;
newRow["OrderQuantity"] = 3;
newRow["CompanyName"] = "NewCompanyName";
newRow["Date"] = "1979, 1, 31";
// Add the row to the rows collection.
table.Rows.Add(newRow);
DataRow newRow2 = table.NewRow();
newRow2["OrderID"] = 2;
newRow2["OrderQuantity"] = 2;
newRow2["CompanyName"] = "NewCompanyName1";
table.Rows.Add(newRow2);
DataRow newRow3 = table.NewRow();
newRow3["OrderID"] = 3;
newRow3["OrderQuantity"] = 2;
newRow3["CompanyName"] = "NewCompanyName2";
table.Rows.Add(newRow3);
DataRow[] foundRows;
Console.WriteLine("Original table's CompanyNames");
Console.WriteLine("************************************");
foundRows = table.Select();
// Print column 0 of each returned row.
for (int i = 0; i < foundRows.Length; i++)
Console.WriteLine(foundRows[i][2]);
// Presuming the DataTable has a column named Date.
string expression = "Date = '1/31/1979' or OrderID = 2";
// string expression = "OrderQuantity = 2 and OrderID = 2";
// Sort descending by column named CompanyName.
string sortOrder = "CompanyName ASC";
Console.WriteLine("\nCompanyNames data for Date = '1/31/1979' or OrderID = 2, sorted CompanyName ASC");
Console.WriteLine("************************************");
// Use the Select method to find all rows matching the filter.
foundRows = table.Select(expression, sortOrder);
// Print column 0 of each returned row.
for (int i = 0; i < foundRows.Length; i++)
Console.WriteLine(foundRows[i][2]);
Console.ReadKey();
}
}
}
Output
try this:
DataTable DT = new DataTable();
DataTable sortedDT = DT;
sortedDT.Clear();
foreach (DataRow row in DT.Select("", "DiffTotal desc"))
{
sortedDT.NewRow();
sortedDT.Rows.Add(row);
}
DT = sortedDT;
Yes the above answers describing the corect way to sort datatable
DataView dv = ft.DefaultView;
dv.Sort = "occr desc";
DataTable sortedDT = dv.ToTable();
But in addition to this, to select particular row in it you can use LINQ and try following
var Temp = MyDataSet.Tables[0].AsEnumerable().Take(1).CopyToDataTable();
I have a non empty datatable . What is the best way to add another column to it that has sequential numbering starting from 1.
I tried the following code. But did not work.
DataColumn dc = new DataColumn("Col1");
dc.AutoIncrement = true;
dc.AutoIncrementSeed = 1;
dc.AutoIncrementStep = 1;
dc.DataType = typeof(Int32);
dt.Columns.Add(dc);
Will setting any expression help in this scenario ?
Thanks in Advance
I think you could achieve that by using a 2nd "helper" data table that would contain just an auto-increment field and then you populate/merge it with the existing data, something like this:
DataTable dtIncremented = new DataTable(dt.TableName);
DataColumn dc = new DataColumn("Col1");
dc.AutoIncrement = true;
dc.AutoIncrementSeed = 1;
dc.AutoIncrementStep = 1;
dc.DataType = typeof(Int32);
dtIncremented.Columns.Add(dc);
dtIncremented.BeginLoadData();
DataTableReader dtReader = new DataTableReader(dt);
dtIncremented.Load(dtReader);
dtIncremented.EndLoadData();
And then you would just return dtIncremented table instead of the original dt. Not an elegant solution but should work.
below code worked for me
Code is Edited
// Added temp rows so that this solution can mimic actual requirement
DataTable dt = new DataTable();
DataColumn dc1 = new DataColumn("Col");
dt.Columns.Add(dc1);
for(int i=0;i<10;i++)
{
DataRow dr = dt.NewRow();
dr["Col"] = i.ToString();
dt.Rows.Add(dr);
}
// Added new column with Autoincrement,
DataColumn dc = new DataColumn("Col1");
dc.AutoIncrement = true;
dc.AutoIncrementSeed = 1;
dc.DataType = typeof(Int32);
// Handeled CollectionChanged event
dt.Columns.CollectionChanged += new CollectionChangeEventHandler(Columns_CollectionChanged);
dt.Columns.Add(dc);
// After column added demostratation
DataRow dr1 = dt.NewRow();
dt.Rows.Add(dr1);
void Columns_CollectionChanged(object sender, CollectionChangeEventArgs e)
{
DataColumn dc = (e.Element as DataColumn);
if (dc != null && dc.AutoIncrement)
{
long i = dc.AutoIncrementSeed;
foreach (DataRow drow in dc.Table.Rows)
{
drow[dc] = i;
i++;
}
}
}
You'll have to build a whole new datatable for this and manually deep-copy each row one by one from the old table to the new. Sorry.