从DataTable中删除列表中不存在的行

Question

I have a dynamic list that contains the names of columns

 var newList = new List<string>(){ "ColName1", "ColName2", "ColName3", "ColName4" };

I also have a datatable that has these column names. However this datatable needs to match my list so if there are columns in this datatable that do not exist in the list then it needs to be removed. How can I do that? So far this is what i have

      DataTable sourceData = new DataTable();
      List<DataRow> rowsToDelete = new List<DataRow>();

                foreach (DataRow row in sourceData.Rows)
                {
                    if (!newList.Contains(row[""].ToString())) //Errors here as the names cannot be hardcoded. It needs to be dynamic
                    {
                        rowsToDelete.Add(row);
                    }
                }

                foreach (DataRow row in rowsToDelete)
                {
                    sourceData.Rows.Remove(row);
                }

                sourceData.AcceptChanges();

Answer 1

You could simply remove them like:

foreach(string col in newList)
    if(sourceData.Columns.Contains(col))
         sourceData.Columns.Remove(col);

But however it's better not to include them in your query in the first place:

string query = $"select {string.Join(",", newList)} from someTable";

Answer 2

I'm not sure why you're checking if columns exist on a DataRow , they are defined on the DataTable , but this would work:

if (row.Table.Columns.Cast<DataColumn>().Any(x => !newList.Contains(x.ColumnName)))
{
    rowsToDelete.Add(row);
}