Develop Reference

copy only the first column with data from one DataTable to another new DataTable

My DataTable has many columns more than 35 columns. Among them I want to copy the first column "SYMBOL_QA" data to another new DataTable.
I searched in internet but did not found any suitable approaches. One approach I found was to copy the whole DataTable as it is, then delete the unwanted columns. But I have 35 columns and deleting all of them one by one will not be good approach.
protected void SendDataTable(DataTable dSource)
{
DataTable dTarget = new DataTable();
dTarget.Columns.Add(new DataColumn("SYMBOL_QA_"));
int rowIdx = 0;
dTarget.AsEnumerable().All(row => { row["SYMBOL_QA_"] = dSource.Rows[rowIdx++]["SYMBOL_QA"]; return true; });
}
This code block is not working. How can I do this ?

I think that the easiest method to do what you have requested is through the DataView.ToTable method
DataTable dTarget = dSource.DefaultView.ToTable(false, "SYMBOL_QA");
It is just a single line and it
Creates and returns a new DataTable based on rows in an existing
DataView.

protected DataTable CopyColumn(DataTable sourceTable, string columnName)
{
DataTable result = new DataTable();
result.Columns.Add(new DataColumn(columnName));
foreach(DataRow sourceRow in sourceTable.Rows)
{
var destRow = result.NewRow();
destRow[columnName] = sourceRow[columnName];
result.Rows.Add(destRow);
}
return result;
}

Check if row exists in DataTable?

I have a datatable and a row. I want to import the row to the datatable only if it does not exist in the datatable.
How can i do that?

If you use a typed DataSet, I.e. declared in design time, the "linq Contains method" takes a typed DataRow. The default IEqualityComparer will compare all values in the DataRow. (Which is normally useless, since you should have a key defined).
DataSet1 ds = new DataSet1();
DataSet1.DataTable1Row row = ds.DataTable1.AddDataTable1Row(bla, bla);
bool exists = ds.DataTable1.Contains(row);

You can use LINQ to check if row is present in datatable. Follow this solution, and replace "id" with your row's primary key, by which you can uniquely identify a row in a table.
DataRow dr = null; // assign your DR here
DataTable dt = new DataTable(); // assign Datatable instance here.
var k = (from r in dt.Rows.OfType<DataRow>() where r["id"].ToString() == dr["id"].ToString() select r).FirstOrDefault();
if(k != null)
{ // Row is present }

if you want to check all the cells in a DataRow, you can try this function:
bool ContainDataRowInDataTable(DataTable T,DataRow R)
{
foreach (DataRow item in T.Rows)
{
if (Enumerable.SequenceEqual(item.ItemArray, R.ItemArray))
return true;
}
return false;
}

you can use Contains as below
if(DataTable.Columns.Contains("RowName"))
{
//Do some stuffs here
}

Tried all answers here but did not work, so I made something for myself which works in my case. The code is pretty simple, it checks if the row you want to add already exists in the datatable - if it does not exist in the datatable, add it.
// fill dt with information
DataTable dt = new DataTable();
// create a new row and fill it with information
DataRow dr = dt.NewRow();
// distinct
bool isDistinct = true;
for (int i=0; i < dt.Rows.Count; i++)
{
// check if both rows are equal
if (Enumerable.SequenceEqual(dt.Rows[i].ItemArray, dr.ItemArray))
{
// it already exists
isDistinct = false;
break;
}
}
if (isDistinct)
{
dt.Rows.Add(dr);
}

if ( Datatable1.Rows[NumOfRow].ToString().Deleted == "Deleted")

You should check row existence by comparing primary keys:
static bool RowExists(DataTable table, DataRow row)
{
var pk = table.PrimaryKey
.Select(column => row[column, DataRowVersion.Original])
.ToArray();
return table.Rows.Contains(pk);
}
Reason is, DataRow that you are trying to check against existing DataTable is, in real-life scenarios, different class instance compared to the DataRaw in the table, even when same DataRaw already exists in the DataTable. Usual .NET equality-comparison does not work properly in this scenarios. That includes DataTable.Contains(...) method.
To properly check for DataRaw existence in the table, primary key given DataRaw should be searched for in the table.

You can check using any with the key value
If (value.Tables(0).AsEnumerable().Any(Function(x) key = x.Field(Of Integer)("ProductId") ))

How to Create sub DataTable from an existing DataTable

I have a DataTable(dataTable1) that have 25-30 columns. I want to bind a DataGridView by creating a small DataTable (dataTable2) that will have few columns (may 5-10) from the existing DataTable.
So my main task is to create a DataTable with fewer columns from the existing one.
Here is the code what I have tried so for..
DataTable subDataTable()
{
DataTable smallTable=new DataTable();
smallTable =dataTable1;// dataTable1 is already filled with data
smallTable.Columns.Remove("Column2");
smallTable.Columns.Remove("Column5");
smallTable.Columns.Remove("Column6");
smallTable.Columns.Remove("Column13");
smallTable.Columns.Remove("Column16");
return smallTable;
}
Its working fine. But I'm looking if there any better way.

You can try to convert your DataTable to IEnumerable,and Select necessary fields with linq like this:
var myValues = dataTable1.AsEnumerable()
.Select(x => new { col1 = x["Column1"], col2 = x["Column2"]..});
dataGridView.DataSource = myValues;

Your code will not work because you all you do is assign a variable smallTable with reference to dataTable1 and you removing columns from your original table object
Linq is faster to write but here is what you want to do to understand your issue:
DataTable smallTable = dataTable1.Clone(); // Copy data structure
// Now you can remove your columns
smallTable.Columns.Remove("Column2");
......
foreach (var row in dataTable1.Rows) // iterate all rows
{
var newRow = smallTable.NewRow();
foreach (var col in smallTable.Columns) // and iterate only needed columns
{
newRow[col.ColumnName] = row[col.ColumnName];
}
}
This is pretty much what sugar-coated by Linq

DataView dv = new DataView(dataTable1);
DataTable smallTable = dv.ToTable(true, new string[] { "Column2", "Column5"...});
https://social.msdn.microsoft.com/Forums/en-US/ac2c7c95-66d6-4db6-a6fb-4dccd5fa701e/is-there-a-better-way-to-get-subtable-with-selected-columns-of-a-datatable?forum=adodotnetdataset
Tomer.

Merging DataTables with Condition

I would like to merge DataTables in a list using sum or average depending on conditions. For example:
private DataTable getData(List<DataTable> datas, string[] KeyColumnNames, string valueCol)
{
List<DataTable> dataTables = datas;
//if datas has 3 dataTables in it : dt1, dt2, dt3
// then I want to create another dataTable dtAll which will have the sum of
// valueCol of all three datatables for the row which will be conditioned using
// KeyColumnNames (can be multiple Primary keys)
return dataTable;
}
Consider all datatables to be exactly same but different values as they are tables from similar schemas but different data centers.
Thanks.

I would do
List<DataTable> dataTableList = dtList;
DataTable unionDataTable = new DataTable();
for(int i = 0; i < dtList.Count; i++)
unionDataTable = Union(unionDataTable, dtList[i], "UnionDataTable");
where the Union method is defined by something like the following
public static DataTable Union(DataTable First, DataTable Second, string strReturnedTableName)
{
// Result table.
DataTable table = new DataTable(strReturnedTableName);
// Build new columns.
DataColumn[] newcolumns = new DataColumn[First.Columns.Count];
for (int i = 0; i < First.Columns.Count; i++)
newcolumns[i] = new DataColumn(First.Columns[i].ColumnName, First.Columns[i].DataType);
// Add new columns to result table.
table.Columns.AddRange(newcolumns);
table.BeginLoadData();
// Load data from first table.
foreach (DataRow row in First.Rows)
table.LoadDataRow(row.ItemArray, true);
// Load data from second table.
foreach (DataRow row in Second.Rows)
table.LoadDataRow(row.ItemArray, true);
table.EndLoadData();
return table;
}
I hope this helps.
Edit. You can pass an Action in to the method and use this in the foreach blocks to do what you want.

Your question is way too vague to provide any actual code but you want to do a LINQ Join. It works about the same as a SQL join. This question shows joins in both query and method syntax How to do a join in linq to sql with method syntax? also you can look at the msdn docs here; http://msdn.microsoft.com/en-us/library/bb311040.aspx

Delete row from datatable where first column does not contain (some string)

I have DataTable with the following columns:
ClientID date numberOfTransactions price
ClientID is of type string and I need to ensure that its contents include "A-" and "N6" for every value in the table.
I need to delete all rows from the DataTable where this first column (ClientID) does not contain both "A-" and "N6" (some totals and other unnecessary data). How can I select and delete these rows specifically from the DataTable?
I know this:
foreach (DataRow row in table.Rows) // Loop over the rows.
{
//Here should come part "if first column contains mentioned values
}
I also know this
If (string.Contains("A-") == true && string.Contains("N6") == true)
{
//Do something
}
I need help how to implement this for first column of each row.

Try this:
EDIT: Totally messed up that last line, so if you tried it, try it now that I made it not stupid. =)
List<int> IndicesToRemove = new List<int>();
DataTable table = new DataTable(); //Obviously, your table will already exist at this point
foreach (DataRow row in table.Rows)
{
if (!(row["ClientID"].ToString().Contains("A-") && row["ClientID"].ToString().Contains("N6")))
IndicesToRemove.Add(table.Rows.IndexOf(row));
}
IndicesToRemove.Sort();
for (int i = IndicesToRemove.Count - 1; i >= 0; i--) table.Rows.RemoveAt(IndicesToRemove[i]);

try using this,
assuming dt as your Datatabe object and ClientID as your first column (hence using ItemArray[0])
for(int i=0; i<dt.Rows.Count; i++)
{
temp = dt.Rows[i].ItemArray[0].ToString();
if (System.Text.RegularExpressions.Regex.IsMatch(temp, "A-", System.Text.RegularExpressions.RegexOptions.IgnoreCase) || System.Text.RegularExpressions.Regex.IsMatch(temp, "N6", System.Text.RegularExpressions.RegexOptions.IgnoreCase))
{
dt.Rows.RemoveAt(i);
i--;
}
}
Simple and straight forward solution... hope it helps

this should be more efficient, both in lines of Code and Time, try this :)
for(int x=0; x<table.Rows.Count;)
{
if (!table.Rows[x].ItemArray[0].contains("A-") && !table.Rows[x].ItemArray[0].contains("N6"))
table.Rows.RemoveAt(x);
else x++;
}
Happy Coding

Preface: C.Barlow's existing answer is awesome, this is just another route someone could take.
This is one way to do it where you never have to loop all the way through the original table (by taking advantage of the DataTable.Select() method):
DataTable table = new DataTable(); // This would be your existing DataTable
// Grab only the rows that meet your criteria using the .Select() method
DataRow[] newRows = table.Select("ClientID LIKE '%A-%' AND ClientID LIKE '%N6%'");
// Create a new table with the same schema as your existing one.
DataTable newTable = table.Clone();
foreach (DataRow r in newRows)
{
// Dump the selected rows into the table.
newTable.LoadDataRow(r.ItemArray, true);
}
And now you have a DataTable with only the rows you want. If necessary, at this point you could clear out the original table and replace it with the contents of the new one:
table.Clear();
table = newTable.Copy();
Edit: I thought of a memory optimization last night, you can just overwrite the existing table once you have the rows you need, which avoids the need for the temporary table.
DataTable table = new DataTable(); // This would be your existing DataTable
// Grab only the rows that meet your criteria using the .Select() method
DataRow[] newRows = table.Select("ClientID LIKE '%A-%' AND ClientID LIKE '%N6%'");
// Clear out the old table
table.Clear();
foreach (DataRow r in newRows)
{
// Dump the selected rows into the table.
table.LoadDataRow(r.ItemArray, true);
}