Inserting values with if and else statements

im making a WF where i get to insert soccer results, however the team winning should get 3, the losing team 0, if its a draw both should get 0.

i have a DB called voetbaldb, with a table called teams, where the scores of the teams should be updated, with 3 columns called ID which is primary key, teamname and teamrank which is unique.

this is my code, however i just cant get it work, i cant find away to give the winnning team the points it deserves:

  int value;

        if (int.TryParse(txt_box_home_score.Text > txt_box_away_score.Text, out value))
        {
            UPDATE teams SET teamrank = (SELECT ISNULL(MAX(teamrank), 0) + 3 FROM teams) 
        }
        if else (int.TryParse(txt_box_home_score.Text < txt_box_away_score.Text, out value))
        {
            UPDATE teams SET teamrank = (SELECT ISNULL(MAX(teamrank), 0) + 3 FROM teams) 
        }
        else (int.TryParse(txt_box_home_score.Text == txt_box_away_score.Text, out value))
        {
            UPDATE teams SET teamrank = (SELECT ISNULL(MAX(teamrank), 0) +1 FROM teams)
        }