/// <summary>
/// Determine the number of records that exist by filter.
/// </summary>
/// <param name="tableName">The name of the table.</param>
/// <param name="filter">Expression.</param>
/// <returns>The number of records.</returns>
public long Count(string tableName, Expression filter)
{
if (String.IsNullOrEmpty(tableName))
{
throw new ArgumentNullException(nameof(tableName));
}
DataTable result = Query(PostgresqlHelper.CountQuery(tableName, _CountColumnName, filter));
if (result != null &&
result.Rows.Count > 0 &&
result.Rows[0].Table.Columns.Contains(_CountColumnName) &&
result.Rows[0][_CountColumnName] != null &&
result.Rows[0][_CountColumnName] != DBNull.Value)
{
return(Convert.ToInt64(result.Rows[0][_CountColumnName]));
}
return(0);
}
