Develop Reference

How to add a column and values in to existing Data column from a string array

I have to add a data column in to the existing data table.
I need to add one more column and data to that table from a .txt file in to 0th column and from second column I need to keep the DB data.
I am not using any grid view and stream reader to my app. I need to use File.ReadAllLines();
My .txt file is like:
ClaimID
val1
val3
val5
I tried something and the data table is not coming properly. Data table coming like showing in the picture below (data is starting from last row of first column and skipped first rows):
What I have tried is:
if (tableName == "TestData")
{
var pathC = #"H:\claimdetails\claims\Claims.txt";
string[] result = File.ReadAllLines(pathC);
DataColumn Col = table.Columns.Add("Claim_ID", typeof(String));
Col.SetOrdinal(0); // set column to first position
DataRow row;
for (int i = 0; i < result.Length; i++)
{
row = table.NewRow();
row["Claim_ID"] = result[i];
table.Rows.Add(row);
}
}
adapter.Fill(table);
How can I get a proper data table?

Instead of adding rows to the data table, you can try,
table.Rows[i].[0] = result[i]

How to insert a datatable into an existing Database and overwrite duplicates?

I currently have a data table which adds new rows based on the Access table rows. In the data table, I change the value of certain columns and update them back to the database. I want to write a line of code that overwrites the data if the primary key already exists. I already looked into a query INSERT INTO table (id, name, age) VALUES(1, "A", 19) ON DUPLICATE KEY UPDATE name="A", age=19 but I can't find a way to implement this since i'm using a data adapter.
I have made the following code:
for (int i = 1; i < 19; i++)
{
Normen.Clear();
Normen.Add(-1);
for (int j = 9; j < 18; j++)
{
Normen.Add(Convert.ToInt32(NormDb.Rows[j].Field<double>(i)));
}
newRow[i] = Convert.ToInt32(GlobalMethods.LeftSegmentIndex(Normen, Convert.ToInt32(newRow[i + 18])));
}
schoolDb.Rows.Add(newRow);
Normen is in this case a list with integers i use to calculate test scores which are then inserted into the empty columns i fetched from the database table.
when this code runs, i have a datatable with rows and columns which are identical to the database columns. When this code is done, the other method is triggered to update the data into the datatable like this:
using (var dbcommand = new OleDbCommand(ZoekQuery, connection))
{
using (var SchoolAdapter = new OleDbDataAdapter(ZoekQuery, connection))
{
OleDbCommandBuilder cb = new OleDbCommandBuilder(SchoolAdapter);
cb.GetInsertCommand();
SchoolAdapter.FillSchema(schoolDb, SchemaType.Source);
SchoolAdapter.Fill(schoolDb);
Normeringen.Normeer(exportDb.Rows.Count, schoolDb, exportDb, NormDb, normcode);
SchoolAdapter.Update(schoolDb);
MessageBox.Show(Success);
}
}
But when the primary key already exists i want to overwrite the record because in this use case it is possible to grade a test with 2 different values. Is there any way i can implement this?

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);
}

Merge Portions of a data table into one

I have a bunch of data tables (In a list), all with 50 columns.
Say I want to build a new data table with columns 20-29 and 40-49.
and then copy all rows from each data table into the new one. but only those selected columns.
DataTable.Merge() will not work since I only want a subset of the columns.
What's the best way to achieve this goal?

I think simple plain old for loops should do the trick under these conditions
DataTable table = new DataTable();
DataTable existing = listOfTables[0];
for(int i = 20; i < 30; i ++)
{
table.Columns.Add(existing.Column[i].Name;
table.Columns.Add(existing.Column[i + 20].Name;
}
foreach(DataTable table in listOfTables)
{
foreach(DataRow row in table.Rows)
{
DataRow newRow = table.NewRecord();
foreach(Column column in table.Columns)
{
newRow[column.Name] = row[column.Name];
}
table.Rows.Add(row);
}
}
Note
I haven't compiled the code.