how to take average for Varchar data type

one of my column in my table is of type varchar. which contains hexadecimal values. i need to take average for particular month . the below is my query. please help me how to change the code to achieve it.

select avg(hex) from history where Date between '2016-11-01' and '2017-11-29' group by Date;  

Thanks in advance

Answer

You can use CAST to DateTime

 SqlCommand command = new SqlCommand("SELECT Top 1 CAST(TimeStamp AS DATETIME) as TimeStamp  FROM HistoryReport ", conn);

CAST

For example

SELECT CAST('2017/10/10' AS DATETIME)

The filed should be a DateTime string or they will be error

EDIT

A small example for you.

The keyPoint is command.ExecuteReader() get the SQL Query Collection.

string commandText = "SELECT Top 1 CAST(TimeStamp AS DATETIME) as TimeStamp  FROM HistoryReport ";
string connectionString = "your Connection string";
using (SqlConnection connection = new SqlConnection(connectionString))
{
    SqlCommand command = new SqlCommand(commandText, conn);
    try
    {
        connection.Open();
        SqlDataReader reader = command.ExecuteReader();
        while (reader.Read())
        {
            DateTime date = reader[0] as DateTime;
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }
}

SqlCommand