Obtaining a Single Value from a Database (ADO.NET)
You may need to return database information that is simply a single value rather than in the form of a table or data stream. For example, you may want to return the result of an aggregate function such as COUNT(*), SUM(Price), or AVG(Quantity). The Command object provides the capability to return single values using the ExecuteScalar method. The ExecuteScalar method returns, as a scalar value, the value of the first column of the first row of the result set.
The following code example inserts a new value in the database using a SqlCommand. The ExecuteScalar method is used to return the identity column value for the inserted record.
Public Function AddProductCategory( _
ByVal newName As String, ByVal connString As String) As Integer
Dim newProdID As Int32 = 0
Dim sql As String = _
"INSERT INTO Production.ProductCategory (Name) VALUES (@Name); " _
& "SELECT CAST(scope_identity() AS int);"
Using conn As New SqlConnection(connString)
Dim cmd As New SqlCommand(sql, conn)
cmd.Parameters.Add("@Name", SqlDbType.VarChar)
cmd.Parameters("@Name").Value = newName
Try
conn.Open()
newProdID = Convert.ToInt32(cmd.ExecuteScalar())
Catch ex As Exception
Console.WriteLine(ex.Message)
End Try
End Using
Return newProdID
End Function
static public int AddProductCategory(string newName, string connString)
{
Int32 newProdID = 0;
string sql =
"INSERT INTO Production.ProductCategory (Name) VALUES (@Name); "
+ "SELECT CAST(scope_identity() AS int)";
using (SqlConnection conn = new SqlConnection(connString))
{
SqlCommand cmd = new SqlCommand(sql, conn);
cmd.Parameters.Add("@Name", SqlDbType.VarChar);
cmd.Parameters["@name"].Value = newName;
try
{
conn.Open();
newProdID = (Int32)cmd.ExecuteScalar();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
return (int)newProdID;
}
See Also
Concepts
DbConnection, DbCommand and DbException (ADO.NET)