CODEWITHSUNDEEP
c#asp.net
user354547
user354547

Reputation: 775

how to copy only the columns in a DataTable to another DataTable?

how to copy only the columns in a DataTable to another DataTable?

Upvotes: 70

Views: 162339

Answers (6)

Bhasin
Bhasin

Reputation: 23

If you want to copy the DataTable to another DataTable of different Schema Structure then you can do this:

  • Firstly Clone the first DataType so that you can only get the structure.
  • Then alter the newly created structure as per your need and then copy the data to newly created DataTable .

So: 

Dim dt1 As New DataTable
dt1 = dtExcelData.Clone()
dt1.Columns(17).DataType = System.Type.GetType("System.Decimal")
dt1.Columns(26).DataType = System.Type.GetType("System.Decimal")
dt1.Columns(30).DataType = System.Type.GetType("System.Decimal")
dt1.Columns(35).DataType = System.Type.GetType("System.Decimal")
dt1.Columns(38).DataType = System.Type.GetType("System.Decimal")
dt1 = dtprevious.Copy()

Hence you get the same DataTable but revised structure

Upvotes: 1

Chaithanya
Chaithanya

Reputation: 189

If you want the structure of a particular data table(dataTable1) with column headers (without data) into another data table(dataTable2), you can follow the below code:

        DataTable dataTable2 = dataTable1.Clone();
        dataTable2.Clear();

Now you can fill dataTable2 according to your condition. :)

Upvotes: 1

codingbadger
codingbadger

Reputation: 43974

DataTable.Clone() should do the trick. 

DataTable newTable = originalTable.Clone();

Upvotes: 134

qery
qery

Reputation: 39

Datatable.Clone is slow for large tables. I'm currently using this:

Dim target As DataTable = 
    New DataView(source, "1=2", Nothing, DataViewRowState.CurrentRows)
    .ToTable()

Note that this only copies the structure of source table, not the data.

Upvotes: 3

drwatsoncode
drwatsoncode

Reputation: 5223

The DataTable.Clone() method works great when you want to create a completely new DataTable, but there might be cases where you would want to add the schema columns from one DataTable to another existing DataTable.

For example, if you've derived a new subclass from DataTable, and want to import schema information into it, you couldn't use Clone().

E.g.:

public class CoolNewTable : DataTable {
   public void FillFromReader(DbDataReader reader) {
       // We want to get the schema information (i.e. columns) from the 
       // DbDataReader and 
       // import it into *this* DataTable, NOT a new one.
       DataTable schema = reader.GetSchemaTable(); 
       //GetSchemaTable() returns a DataTable with the columns we want.

       ImportSchema(this, schema); // <--- how do we do this?
   }
}

The answer is just to create new DataColumns in the existing DataTable using the schema table's columns as templates.

I.e. the code for ImportSchema would be something like this:

void ImportSchema(DataTable dest, DataTable source) {
    foreach(var c in source.Columns)
        dest.Columns.Add(c);
}

or, if you're using Linq:

void ImportSchema(DataTable dest, DataTable source) {
    var cols = source.Columns.Cast<DataColumn>().ToArray();
    dest.Columns.AddRange(cols);
}

This was just one example of a situation where you might want to copy schema/columns from one DataTable into another one without using Clone() to create a completely new DataTable. I'm sure I've come across several others as well.

Upvotes: 0

freak
freak

Reputation: 483

If only the columns are required then DataTable.Clone() can be used. With Clone function only the schema will be copied. But DataTable.Copy() copies both the structure and data

E.g.

DataTable dt = new DataTable();
dt.Columns.Add("Column Name");
dt.Rows.Add("Column Data");
DataTable dt1 = dt.Clone();
DataTable dt2 = dt.Copy();

dt1 will have only the one column but dt2 will have one column with one row.

Upvotes: 38

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