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Asp.net – Easier way to select a string in EF Core?

I would like to get the value of @@SERVERNAME. The following code works:

[Keyless]
public class EntityString
{
    public String Value { get; set; } = String.Empty;
};

// inside MyDbContext.OnModelCreating
modelBuilder.Entity<EntityString>();

// inside MyDbContext
public IQueryable<EntityString> QueryServerName()
     => Set<EntityString>().FromSqlRaw("SELECT @@SERVERNAME as Value");

// At usage site
ServerName = (await WHContext.QueryServerName().FirstAsync()).Value

However it seems overly complex for the simple task. Is there an easier way to execute a SELECT query that is expected to return a single string value?

Using String instead of EntityString gave a runtime error that an entity class was required .

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2

Answers


  1. Chosen as BEST ANSWER
    0

    The following change worked:

    // In MyDbContext class
public IQueryable<EntityString> QueryServerName()
     => Database.SqlQueryRaw<String>("SELECT @@SERVERNAME as Value").AsQueryable();

// usage 
ServerName = await MyContext.QueryServerName().SingleAsync();

    Using SqlQuery gave an error that string could not be converted to FormattableString.

    Omitting the as Value from the query string gave a runtime error "No column name was specified for column 1 of 't'. Invalid column name 'Value'."


  2. 0

    You can do something like this

    // Inside MyDbContext.OnModelCreating
modelBuilder.Entity<string>().HasNoKey().ToView("ServerName");

// Inside MyDbContext
public async Task<string> GetServerNameAsync()
{
    return await Set<string>().FromSqlRaw("SELECT @@SERVERNAME as 
       Value").FirstOrDefaultAsync() ?? string.Empty;
}

// At usage site
ServerName = await WHContext.GetServerNameAsync();
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