Can I Use Single Function For A Big Project ???...

Hi,

I wnat to write a single function in code behind file for all DML operation, and i just want to pass query string in its parameter. but when ever my whole project will use this function to insert, update and delete. what will be the performance.

 bool DMLoperation(string str)
{

obj.conn = new SqlConnection(obj.connstring);
obj.cmd = new SqlCommand(str,obj.conn);
obj.conn.Open();
try
{
if(obj.cmd.ExecuteNonQuery() > 0)
{
obj.conn.Close();
return true;
}
else
{
obj.conn.Close();
return false;
}
}
catch
{
obj.conn.Close();
return false;
}
} 

I am totally confused about performance, is it good idea or worst ?.