如何从其他数据表的行向数据表添加列

Question

I have a DataTable called dt which is filled with values from excel.

On line 6 (row) i have my header information

Code i have now

   string connString = @"Provider=Microsoft.ACE.OLEDB.16.0;Data Source=C:\Users\thoje\Desktop\stack\forslag.xlsx;" +
        @"Extended Properties=""Excel 12.0;HDR=No;""";
        DataTable dt = new DataTable();

        string sql = @"SELECT * from [Ark1$]";
        using (OleDbConnection conn = new OleDbConnection(connString))
        {
            conn.Open();
            using (OleDbCommand cmd = new OleDbCommand(sql, conn))
            {
                using (OleDbDataReader rdr = cmd.ExecuteReader())
                {
                    dt.Load(rdr);



                }
            }
        }
        DataTable dt2 = dt.Clone();



        //foreach (DataRow dr in dt.Rows)
        //{

        for (int i = 5; i <= dt.Rows.Count-1; i++)
        {


            if (i == 6)
            {
                DataRow dr = dt2.NewRow();
                dr.ItemArray = dt.Rows[i].ItemArray;
                dt2.Rows.Add(dr);

            }


            else if(i >=8)
            {
                DataRow dr = dt2.NewRow();
                dr.ItemArray = dt.Rows[i].ItemArray;
                dt2.Rows.Add(dr);
            }
        }

What i need is:

1. I want all my data on row 6 to become headers in a new DataTable
2. All data after line 7 i need to append to this new Datatable with the new headers.

What my code shows:

My code now shows how to do it on a DataTable which is cloned, so therefore i have the wrong headernames.

Answer 1

You don't need to iterate through all rows if you only need 1 of them.

DataTable dtSource = new DataTable();
DataTable dtTarget = new DataTable();

// Get row at index == 6 (7th line as this is a 0-based-index)
var headerRow = dtSource.Rows[6];

// Iterate through all values
foreach(var value in headerRow.ItemArray)
{
    // For each value create a column
    // and add it to your new dataTable
    DataColumn dc = new DataColumn(value.ToString());
    dc.Caption = value.ToString();
    dtTarget.Columns.Add(dc);
}

Answer 2

using a linq approach might be good: a pseudo way:

 //linq query to select row 
 var query = from myRow in
 myDataTable.AsEnumerable() where myRow.Field<int>("RowNo") == 6 
 select myRow;

// Create a table from the query DataTable newTable =
query.CopyToDataTable<DataRow>();

Answer 3

Your question is pretty confusing to read, and keeps talking about rows where I'd expect columns etc, but I'll make the following assumptions:

• You have an excel file with 5 blank rows and then a row of headers, and then data rows
• You've successfully imported this data into a Datatable called dt
• You want to end up with a datatable that has the values in row 6 as the column names, and the blank rows removed

Code:

for(int i = 5; i >= 0; i--){
  if(i == 5)
  {
    for(int j = 0; j < dt.Columns.Count; j++)
      dt.Columns[j].ColumnName = dt.Rows[i][j].ToString();
  }
  dt.Rows.RemoveAt(i);
}

You don't need to clone the datatable. Watch out for strings that make for poor column names (containing chars like '[' ) making your life miserable further down the line ..