change datatype of a datatable object in c#

I want to change the DataTable type to decimal how to I do that

namespace ReadDataFromCSVFile
{
static class Program
{
static void Main()
{
string csv_file_path = @"C:\Matlab\Sheet1_t168h.csv";
DataTable csvData = GetDataTabletFromCSVFile(csv_file_path);
Console.WriteLine("Rows count:" + csvData.Rows.Count);
Console.ReadLine();
}
private static DataTable GetDataTabletFromCSVFile(string csv_file_path)
{
DataTable csvData = new DataTable();

using (TextFieldParser csvReader = new TextFieldParser(csv_file_path))
{
csvReader.SetDelimiters(new string[] { "," });
csvReader.HasFieldsEnclosedInQuotes = true;
string[] colFields = csvReader.ReadFields();
foreach (string column in colFields)
{
DataColumn datecolumn = new DataColumn(column);
datecolumn.AllowDBNull = true;
csvData.Columns.Add(datecolumn);
}
while (!csvReader.EndOfData)
{
string[] fieldData = csvReader.ReadFields();
//Making empty value as null
for (int i = 0; i < fieldData.Length; i++)
{
if (fieldData[i] == "")
{
fieldData[i] = null;
}
}
csvData.Rows.Add(fieldData);
}
}


return csvData;
}
}
}

Hey Mike, I realize this is really old, but I have a reason that you don't set the type appropriate on the first-go-round. I was loading/parsing a CSV file, and simply added the parsed data to a datatable object, and initially set the column DataType property to object, and then determined the appropriate types from the data in the datatable. It was only after I got all the code in place that I realized you couldn't set the type after the datatable had rows in it, so I create a new method that was called at the end of the processing chain:

protected virtual void SetColumnTypes()
{
    if (this.ColumnHints != null)
    {
        DataTable cloned = this.ImportedData.Clone();
        for (int i = 0; i < cloned.Columns.Count; i++)
        {
            // ColumnHints is an object that determines the datatypes
            // for the imported CSV fields by iterating all of the
            // rows/columns of the initial datatable
            cloned.Columns[i].DataType = ColumnHints[i].ItemType;
        }
        foreach (DataRow row in this.ImportedData.Rows)
        {
            cloned.ImportRow(row);
        }
        this.ImportedData = cloned;
    }
}

So, as you can see, sometimes there is a need.

John, why to use a [foreach] loop to copy data between datatables? You can use [CopyToDataTable()] method instead:

cloned = this.ImportedData.CopyToDataTable();
this.ImportedData = cloned;