I know we can easily do this by a simple loop, but I want to persue this LINQ/Predicate?
string[] columnNames = dt.Columns.?
or
string[] columnNames = from DataColumn dc in dt.Columns select dc.name;
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4 Answers
Try this (LINQ method syntax):
string[] columnNames = dt.Columns.Cast<DataColumn>()
.Select(x => x.ColumnName)
.ToArray();
or in LINQ Query syntax:
string[] columnNames = (from dc in dt.Columns.Cast<DataColumn>()
select dc.ColumnName).ToArray();
Cast is required, because Columns is of type DataColumnCollection which is a IEnumerable, not IEnumerable<DataColumn>. The other parts should be obvious.
answered Feb 17, 2011 at 7:54
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i am a newbie in linq/lamda ex. This looks good. one more question, how can i place condation(where dc.ColumnName != "ABC") in 1 lamda expression. in linq i can use where.– LalitCommented Feb 17, 2011 at 8:14
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Just like this:
string[] columnNames = dt.Columns.Cast<DataColumn>().Where(x => x.ColumnName != "ABC").Select(x => x.ColumnName).ToArray();Commented Feb 17, 2011 at 8:18 -
1@Tizz: Please post it as a new question and include details of your code. But essentially: A DataGrid is not the same as a DataTable. Commented May 17, 2013 at 8:08
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3@FLICKER: Some thinking is still required as a developer. You have a brain. Use it. Commented Nov 22, 2018 at 6:20
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1Ah well. Just look at the votes. Obviously, the problem is with you, not with the code. Go troll somewhere else Commented Nov 22, 2018 at 6:45
Use
var arrayNames = (from DataColumn x
in dt.Columns.Cast<DataColumn>()
select x.ColumnName).ToArray();
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1On my end, this throws two Exceptions: cannot convert from DataColumnCollection to EnumerableRowCollection and DataColumnCollection does not contain a definition for Cast.– user565869Commented Jul 27, 2011 at 15:48
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4@Jon I think you forogot to add 'using System.Linq;' to your usings. I just tested my code and I get the exceptions you mention when 'using System.Linq;' isn't there. Commented Jul 28, 2011 at 13:03
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Doh! You are quite correct; funny, that
usingstatement is automatically added so often, it never occurred to me to check for it.– user565869Commented Aug 3, 2011 at 15:01
I'd suggest using such extension method:
public static class DataColumnCollectionExtensions
{
public static IEnumerable<DataColumn> AsEnumerable(this DataColumnCollection source)
{
return source.Cast<DataColumn>();
}
}
And therefore:
string[] columnNames = dataTable.Columns.AsEnumerable().Select(column => column.Name).ToArray();
You may also implement one more extension method for DataTable class to reduce code:
public static class DataTableExtensions
{
public static IEnumerable<DataColumn> GetColumns(this DataTable source)
{
return source.Columns.AsEnumerable();
}
}
And use it as follows:
string[] columnNames = dataTable.GetColumns().Select(column => column.Name).ToArray();
List<String> lsColumns = new List<string>();
if(dt.Rows.Count>0)
{
var count = dt.Rows[0].Table.Columns.Count;
for (int i = 0; i < count;i++ )
{
lsColumns.Add(Convert.ToString(dt.Rows[0][i]));
}
}
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