Przechwytywanie liczyć z kwerendy SQL

Question

Jaki jest najprostszy sposób w C# (plik .cs), aby uzyskać liczyć od polecenia SQL

SELECT COUNT(*) FROM table_name 

do zmiennej int?

Answer 1

Zastosowanie SqlCommand.ExecuteScalar() i oddać go do 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

dostaniesz konwersji błędy z

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

użytku zamiast

 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

Uzupełniając w C# z 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