DataContext always ReadOnly, even though a primary key exists

Question

I'm attempting to update a value in my Database, but the IsReadOnly property is always coming back as True. According to Microsoft, that property

Gets a value that indicates whether the type of the entities contained in this Table instance has a primary key

The problem is, my DB DOES have a PK set.

DB definition:

CREATE TABLE TestTable ( ID int NOT NULL PRIMARY KEY, Value varchar(50) NOT NULL ); INSERT INTO TestTable (ID, Value) VALUES (1, '6caaef02-fc34-4112-9574-4c5923c5624d');

LINQ object definition:

[Table( Name = "TestTable" )] public class TestTable { [Column] public int ID { get; set; } [Column] public string Value { get; set; } }

The modification code:

DataContext db = new DataContext(ConnStr); // Just a standard SQL Server connection string var b = db.GetTable<TestTable>().IsReadOnly; // Always 'True' var firstResult = db.GetTable<TestTable>().FirstOrDefault(); Console.WriteLine( firstResult.ID + " " + firstResult.Value ); // The current DB value logs here correctly firstResult.Value = Guid.NewGuid().ToString(); db.GetTable<TestTable>().Single(c => c.ID == 1).Value = Guid.NewGuid().ToString(); var x = db.GetChangeSet(); // Always {{Inserts: 0, Deletes: 0, Updates: 0}} db.SubmitChanges(ConflictMode.FailOnFirstConflict);

No exceptions are thrown, it just doesn't do anything either.

Can anyone tell me what I'm missing here?

[Column(IsPrimaryKey = true)] public int ID { get; set; }? — Svyatoslav Danyliv
– Svyatoslav Danyliv, Commented Dec 4, 2023 at 18:24
@Svyatoslav Danyliv That works! Please turn it into an answer. — Alpocalypse
– Alpocalypse, Commented Dec 4, 2023 at 18:47

Svyatoslav Danyliv · Accepted Answer · 2023-12-04 18:53:15Z

ColumnAttribute has property IsPrimaryKey in which indicates PrimaryKey. LINQ to SQL do not check database for PK while running queries. Mapping should be set by attributes.

[Table( Name = "TestTable" )] public class TestTable { [Column(IsPrimaryKey = true)] public int ID { get; set; } [Column] public string Value { get; set; } }

Piotr · Accepted Answer · 2023-12-04 18:36:15Z

looks like you're used db-first approach, and you model your entity manually.

if you want stay with manual modeling, try with setting [Key] attribute for ID property, that will indicate it's PK. - https://www.entityframeworktutorial.net/code-first/key-dataannotations-attribute-in-code-first.aspx
- I think there is no need to add empty [Column] attribute - https://www.entityframeworktutorial.net/code-first/column-dataannotations-attribute-in-code-first.aspx
Second way - try to generate model/s automatically with tool - https://www.entityframeworktutorial.net/entityframework6/create-entity-data-model.aspx

This question is not related to EF. Before EF, LINQ To SQL was a first LINQ provider which worked only with SQL Server.

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