c# - Why is DataRow not found in DataTable

Question

New to data manipulation using DataTable, DataColumn, DataRow. Why is employee not found in the DataTable? I was expected indexFound to have the value "2", and when I debug the values all look correct.

// Manually create a new DataTable
DataTable dtEmployees = new DataTable("Employee");

// Add columns
dtEmployees.Columns.Add("ID", typeof(int));
dtEmployees.Columns.Add("Name", typeof(string));
dtEmployees.Columns.Add("Salary", typeof(int));

// Add rows to the table
dtEmployees.Rows.Add(52, "Sally", 29000);
dtEmployees.Rows.Add(63, "Harry", 22000);
dtEmployees.Rows.Add(72, "Alain", 23000);
dtEmployees.Rows.Add(110, "Pete", 24500);

// Look for an employee...
int index = 2;
Console.WriteLine("(index of DataRow({0}) should return {0})", index);
DataRow employee = dtEmployees.NewRow();
employee["ID"] = dtEmployees.Rows[index]["ID"];
employee["Name"] = dtEmployees.Rows[index]["Name"];
employee["Salary"] = dtEmployees.Rows[index]["Salary"];

int indexFound = dtEmployees.Rows.IndexOf(employee);
if (indexFound != -1)
    Console.Write("  Employee has index {0}", indexFound); // Was expecting this...
else
    Console.Write("  Employee not found in table..."); // ...but actually get this. Why??

The Microsoft documentation didn't provide any meaningful help.

question from:https://stackoverflow.com/questions/65944204/why-is-datarow-not-found-in-datatable

Answer 1

A DataRow needs to be added to the Rows collection of the Datatable if you want to find it in the collection with IndexOf, so you just need to add this line before searching the row

dtEmployees.Rows.Add(employee);

Of course this method (IndexOf) is of some value only if you have a row to search for. Usually if you want to search a Datatable the preferred way is through the Select method that could return a set of one or more rows using a search criteria that resembles a WHERE sql statement.

dtEmployees.Rows.Add(employee);
DataRow[] rows = dtEmployees.Select("ID = 72");
if(rows != null && rows.Length > 0)
{
     Console.WriteLine("rows found:" + rows.Length);
     foreach(DataRow r in rows)
        Console.WriteLine(r.Field<string>("name"));
}