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

how to copy only the columns i开发者_StackOverflow中文版n a DataTable to another DataTable?

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DataTable.Clone() should do the trick.

DataTable newTable = originalTable.Clone();

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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.

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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.

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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. :)

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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

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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.