Capturer le nombre à partir d'une requête SQL

Question

Quel est le moyen le plus simple en C# (fichier .cs) d'obtenir le nombre à partir de la commande SQL

 SELECT COUNT(*) FROM table_name

dans une variable int

Answer 1

Utilisez SqlCommand.ExecuteScalar() et transmettez-le en int :

 cmd.CommandText = "SELECT COUNT(*) FROM table_name";
Int32 count = (Int32) cmd.ExecuteScalar();

Answer 2

SqlConnection conn = new SqlConnection("ConnectionString");
conn.Open();
SqlCommand comm = new SqlCommand("SELECT COUNT(*) FROM table_name", conn);
Int32 count = (Int32) comm .ExecuteScalar();

Answer 3

Vous obtiendrez des erreurs de conversion avec :

 cmd.CommandText = "SELECT COUNT(*) FROM table_name";
Int32 count = (Int32) cmd.ExecuteScalar();

Utilisez à la place :

 string stm = "SELECT COUNT(*) FROM table_name WHERE id="+id+";";
MySqlCommand cmd = new MySqlCommand(stm, conn);
Int32 count = Convert.ToInt32(cmd.ExecuteScalar());
if(count > 0){
    found = true; 
} else {
    found = false; 
}

Answer 4

Complément en C# avec SQL :

 SqlConnection conn = new SqlConnection("ConnectionString");
conn.Open();
SqlCommand comm = new SqlCommand("SELECT COUNT(*) FROM table_name", conn);
Int32 count = Convert.ToInt32(comm.ExecuteScalar());
if (count > 0)
{
    lblCount.Text = Convert.ToString(count.ToString()); //For example a Label
}
else
{
    lblCount.Text = "0";
}
conn.Close(); //Remember close the connection

Answer 5

int count = 0;    
using (new SqlConnection connection = new SqlConnection("connectionString"))
{
    sqlCommand cmd = new SqlCommand("SELECT COUNT(*) FROM table_name", connection);
    connection.Open();
    count = (int32)cmd.ExecuteScalar();
}