How to 'foreach' a column in a DataTable using C#?

This should work:

DataTable dtTable;

MySQLProcessor.DTTable(mysqlCommand, out dtTable);

// On all tables' rows
foreach (DataRow dtRow in dtTable.Rows)
{
    // On all tables' columns
    foreach(DataColumn dc in dtTable.Columns)
    {
      var field1 = dtRow[dc].ToString();
    }
}

I believe this is what you want:

DataTable dtTable = new DataTable();
foreach (DataRow dtRow in dtTable.Rows)
{
    foreach (DataColumn dc in dtRow.ItemArray)
    {

    }
}

You can check this out. Use foreach loop over a DataColumn provided with your DataTable.

 foreach(DataColumn column in dtTable.Columns)
 {
     // do here whatever you want to...
 }

You can do it like this:

DataTable dt = new DataTable("MyTable");

foreach (DataRow row in dt.Rows)
{
    foreach (DataColumn column in dt.Columns)
    {
        if (row[column] != null) // This will check the null values also (if you want to check).
        {
               // Do whatever you want.
        }
     }
}