I have a table that contains a maximum value that needs to be get and set by multiple programs. How can I lock the table for a while when old value is got and new is updated in C#? In other words:

string sql = "lock table MaxValueTable in exclusive mode";  
using (DbCommand cmd = cnctn.CreateCommand())
{
    cmd.CommandText = sql;
    // execute command somehow!!
}

maxValue = GetMaxValue();
SetMaxValue(maxValue + X);

sql = "lock table MaxValueTable in share mode";  
using (DbCommand cmd = cnctn.CreateCommand())
{
    cmd.CommandText = sql;
    // execute command somehow!!
}