Check if value exists in dataTable?

I have DataTable with two columns Author and Bookname.

I want to check if the given string value Author already exists in the DataTable. Is there some built in method to check it, like for Arrays array.contains?

You can use LINQ-to-DataSet with Enumerable.Any:

String author = "John Grisham";
bool contains = tbl.AsEnumerable().Any(row => author == row.Field<String>("Author"));

Another approach is to use DataTable.Select:

DataRow[] foundAuthors = tbl.Select("Author = '" + searchAuthor + "'");
if(foundAuthors.Length != 0)
{
    // do something...
}

Q: what if we do not know the columns Headers and we want to find if any cell value PEPSI exist in any rows'c columns? I can loop it all to find out but is there a better way? –

Yes, you can use this query:

DataColumn[] columns = tbl.Columns.Cast<DataColumn>().ToArray();
bool anyFieldContainsPepsi = tbl.AsEnumerable()
    .Any(row => columns.Any(col => row[col].ToString() == "PEPSI"));

You can use Linq. Something like:

bool exists = dt.AsEnumerable().Where(c => c.Field<string>("Author").Equals("your lookup value")).Count() > 0;

DataRow rw = table.AsEnumerable().FirstOrDefault(tt => tt.Field<string>("Author") == "Name");
if (rw != null)
{
// row exists
}

add to your using clause :

using System.Linq;

and add :

System.Data.DataSetExtensions

to references.

You should be able to use the DataTable.Select() method. You can us it like this.

if(myDataTable.Select("Author = '" + AuthorName.Replace("'","''") + '").Length > 0)
    ...

The Select() funciton returns an array of DataRows for the results matching the where statement.