C#

foreach(record in records) {
    if (record!=whatWeWant) insert(newRecord);
}

bool exists=false;
foreach(record in records) {
    if(record==whatWeWant) exists=true;
}
if (!exists) insert(newRecord);

SELECT COUNT(1) FROM dbo.tablename WHERE FullName = @ValueWeSearch

SqlCommand selectname = new SqlCommand("SELECT COUNT(*) FROM dbo.SysIdent WHERE FullName = @SysIdent", IdentSys);
                    selectname.Parameters.Add("@SysIdent", SqlDbType.NVarChar, 150);
                    selectname.Parameters["@SysIdent"].Value = SysIdent;
                    IdentSys.Open();
                    selectname.ExecuteNonQuery();
                    int Count = Convert.ToInt32(selectname.ExecuteScalar());
                    if (Count == 0)
{
     // insert new record
}

Luc Pattyn wrote:

3. Your Convert.ToInt32() can be simplified to a simple cast using
(int)

MERGE sometable
USING (select something FROM table) ON (value = @value)
WHEN NOT MATCHED THEN INSERT VALUES (...)

Pete O'Hanlon wrote:

I would also change your insert statement to include the SELECT COUNT as part of the where clause

try
    {
        string c = System.Environment.MachineName;
        string Domain = System.Net.Dns.GetHostName();
        ManagementObjectSearcher SerialNo = new ManagementObjectSearcher("root\\CIMV2", "SELECT * FROM_ 
        Win32_SystemEnclosure");
        foreach (ManagementObject querySN in SerialNo.Get())
        {
            string SN = (querySN["SerialNumber"].ToString());
            string SysIdent = c + SN + "@" + Domain;
    
            using(SqlConnection IdentSys = new SqlConnection(some connection;connection timeout=30"));
            using(SqlCommand selectname = new SqlCommand("SELECT COUNT(1) FROM dbo.SysIdent WHERE_              
                FullName = @SysIdent", IdentSys));
            selectname.Parameters.Add("@SysIdent", SqlDbType.NVarChar, 150);
            selectname.Parameters["@SysIdent"].Value = SysIdent;
            IdentSys.Open();
            int Count = (int)(selectname.ExecuteScalar());
            if (Count == 0)
            {
                using(SqlConnection InsertSys = new SqlConnection(some other connection_;connection
                    timeout=30"));
                using(SqlCommand newname = new SqlCommand("INSERT INTO dbo.SysIdent(FullName)_
                VALUES(@FullName)", InsertSys);
                newname.Parameters.AddWithValue("@FullName", SysIdent);
                InsertSys.Open();
                newname.ExecuteNonQuery();
                InsertSys.Close();
            }
            IdentSys.Close();
            using (SqlConnection selectID = new SqlConnection(another connection;connection timeout=30");
            SqlCommand GetID = new SqlCommand("SELECT * FROM dbo.SysIdent WHERE FullName = @SysIdent", selectID);
            GetID.Parameters.Add("@SysIdent", SqlDbType.NVarChar, 150);
            GetID.Parameters["@SysIdent"].Value = SysIdent;
            selectID.Open();
            SqlDataReader GetmyID = GetID.ExecuteReader();
            while (GetmyID.Read())
            {
                int myID = (int)(GetmyID["ID"]);
                Console.WriteLine(myID);
                Console.ReadLine();
                int mySysId = myID;
                if (!EventLog.SourceExists("mylog")) EventLog.CreateEventSource("mylog", "Application");
                EventLog.WriteEntry("mylog", "ID" + mySysId + " allocated");
            }
        }
    }
    catch (Exception f)
    {
        if (!EventLog.SourceExists("mylog")) EventLog.CreateEventSource("mylog", "Application");
        EventLog.WriteEntry("mylog", "Unable to allocate SysID" + f.ToString());
    }