System.InvalidOperationException: 'No row is available' in PostgreSQL
Dung Do Tien
Jul 21 2021
227
I have created a small project with .Net Core 3.1 C# and PostgreSQL. I want to get an object of backlink table as below:
using (var db = new PostgresSQL(ConnectionString))
{
var query = new StringBuilder();
query.Append("SELECT * ");
query.Append("FROM public.backlink a WHERE a.id = :_id; ");
using (var command = db.CreateCommand(query.ToString(), false))
{
command.Parameters.Add(new NpgsqlParameter("@_id", id));
using (var reader = command.ExecuteReader())
{
if (reader.HasRows)
{
ret.id = (int)reader["id"];
ret.anchortext = reader["anchortext"] + "";
ret.titleseo = reader["titleseo"] + "";
}
}
}
}
But when call this method I got an error: System.InvalidOperationException: 'No row is available'
{System.InvalidOperationException: No row is available
at Npgsql.NpgsqlDataReader.CheckRow()
at Npgsql.NpgsqlDataReader.GetValue(Int32 ordinal)
I was debugging but reader.HasRows always true. I don't know why.
How can I fix it?
Have 2 answer(s) found.
-
f0
fahmi zaki Jul 21 2021
Try adding a
reader.Read()call.using (var reader = await cmd.ExecuteReaderAsync()) { reader.Read() // <== ADD THIS LINE var rowParser = reader.GetRowParser<test>(typeof(test)); result.Add(rowParser(reader)); }Good luck!!
-
M-1
Minh Vĩnh Jul 21 2021
You have to call while
dr.Read();to help read a row like this:if (reader.HasRows) { reader.Read(); ret.id = (int)reader["id"]; ret.anchortext = reader["anchortext"] + ""; }And it works for you.
* Type maximum 2000 characters.
* All comments have to wait approved before display.
* Please polite comment and respect questions and answers of others.