public override string CreateRandomOrderBySql(DataEntityMapping mapping)
{
Random rnd = new Random(unchecked ((int)DateTime.Now.Ticks));
int intRandomNumber = rnd.Next() * -1;
string field = "";
foreach (DataFieldMapping df in mapping.GetFieldMappings())
{
if (df.ObjectType == typeof(int))
{
field = CreateDataFieldSql(df.Name);
break;
}
}
if (string.IsNullOrEmpty(field))
{
foreach (DataFieldMapping df in mapping.GetFieldMappings())
{
if (df.ObjectType == typeof(string))
{
field = string.Format("len({0})", CreateDataFieldSql(df.Name));
break;
}
}
}
if (string.IsNullOrEmpty(field))
{
throw new LightDataException(RE.TypfOfDataFieldIsNotString);
}
return(string.Format("rnd({0}*{1})", intRandomNumber, field));
}