I have an solution using EntityFramework. Im able to save data to the Backend SQL DB and all is well. But when I try to check is a record exist using the statement below im getting an error "Sequence contains more than one matching element."

 var status = await dbContext.Item.AnyAsync(x => x.Name == "Bread")

I’m not sure what’s causing this. Any help appreciated

CodePudding user response：

Sequence contains more than one matching element._"

• If you want to retrieve single object ,use

var status = await dbContext.Item.FirstOrDefaultAsync(x => x.Name == "Bread");

• If you want to retrieve list , then use

 var status  = await dbContext.Item.Where(x => x.Name == "Bread").ToListAsync();

• Use First () or FirstOrDefault() wherever a single value from a collection or database is required.
• Use Single / SingleOrDefault() if you are sure that there is only one record in the database, or if you are querying the db using primary key.

Single() - If no result is returned or if there are more than one results, an exception is raised.

SingleOrDefault() - Same as Single(), but can also handle null values.

First() - If no results are returned, an exception is thrown ,or else at least one result is returned.

FirstOrDefault() - When there is no result, FirstOrDefault() returns null instead of throwing an exception as First() does.

• If your query returns more than one element, SingleOrDefault throws the exception

Sequence contains more than one matching element

FirstOrDefault ignores the second element and returns the first.

• Use FirstOrDefault() instead of SingleOrDefault()

Please refer Enumerable.Single and Enumerable.First for more information

CodePudding user response：

This is not an error that should come back from AnyAsync. I suspect there is something in the structure of your items (e.g. via a foreign key) that is generating the error. Use ToTraceString() to find out the underlying SQL query.