Question

I want to get the value for Column B in the first row I find with Column A = “123”.

I tried:

dataTable.AsEnumerable().Select(row => row["value"].ToString() == "123").ToString();

But I’m getting Expression cannot contain lambda expressions.

Any help would be appreciated, thanks.

EDIT:

I’m basically looking for the SQL equivalent of:

Select ColumnB
From MyTable
Where ColumnA = '123'

For the datatable using a lambda expression.

Answer 1

Take a look at the FirstOrDefault method:

var foundRow = dataTable.AsEnumerable().FirstOrDefault(row => string.Equals (row["ColumnA"].ToString(), "123", StringComparison.OrdinalIgnoreCase ));
if (foundRow != null) {
    // We found a match, do something with it.
    var colBValue = foundRow["ColumnB"].ToString(); 
}

FirstOrDefault returns the first element that matches a specified criteria, which in this case looks for the string “123” in the [ColumnA] column in your DataTable. If no element matches the criteria, FirstOrDefault returns the object’s default value which for DataTable is null.

I don’t know why you are getting the Exception you show, I didn’t when I tried to reproduce it.