How to insert old record to new entity?-CodePudding

I am trying to check record , if exists declare to data with old one . But if doesnt then create a new one. Here is my code ;

var teamCheck= FootballerDBContext.Teams.Any(r => r.Name == teamName.Text.Trim());

if (teamCheck)
                {
                    team = FootballerDBContext.Teams.FirstOrDefault(c => c.Name == teamName.Text);
                
                }
FootballerDBContext.Teams.Add(team);
FootballerDBContext.SaveChanges(); // throwing exception right there . I did it exactly same to other entity everything was fine.

Here is other entity , i did the same but Team throws exception. No errors here , doing what i want. It doesnt create new entity with new ID , just declaring old one. ( sponsor has many-to-many relationship , team has one-to-many )

var sponsorCheck = FootballerDBContext.Sponsors.Any(x => x.Name == Sponsor.Text.Trim());
if (sponsorCheck)
                    {
                        sponsor = FootballerDBContext.Sponsors.FirstOrDefault(z => z.Name == Sponsor.Text);
                        
                    }

FootballerDBContext.FootballerSponsor.Add(fbsp);
                        FootballerDBContext.SaveChanges();

CodePudding user response：

Don't do it like you're doing; it queries the database twice

Do a pattern like this instead:

var team = FootballerDBContext.Teams.FirstOrDefault(c => c.Name == teamName.Text.Trim());
            
if(team == default) //or null
{            
    team = new Team(){ Name = teamName.Text };
    FootballerDBContext.Teams.Add(team);
}

team.Location = teamLocation.Text;
...


FootballerDBContext.SaveChanges();

Query using Find or FirstOrDefault
If the result is null make a new one and assign it to the variable that is null
Add the team to the context if you just made a new one
Now you definitely have a team, either because you made it new or because it already exists and is looked up
You can set other properties
Call save changes at the end and an update or insert command will be run as appropriate

CodePudding user response：

These LINQ queries are not the same: teamName.Text.Trim() vs teamName.Text .Trim()

try to check if variable is null or not like this:

string teamName = teamName.Text.Trim()
if (!String.IsNullOrEmpty(teamName)) 
    first: **team** default value is (teamName)
    second: validate linq query... r => r.Name == teamName

if (second == false) 
    save first.