How to get next value of SQL Server sequence in Entity Framework?

To obtain the next value from a SQL Server sequence using Entity Framework, there are a few methods you can employ:

Method 1: Utilizing a Stored Procedure

CREATE PROCEDURE dbo.GetNextSequenceValue 
AS 
BEGIN
    SELECT NEXT VALUE FOR dbo.TestSequence;
END

1. Create a stored procedure named GetNextSequenceValue in SQL Server that retrieves the next sequence value.

// Import the stored procedure into your EDMX model in Entity Framework.
using (YourEfContext ctx = new YourEfContext())
{
    // Call the stored procedure function import.
    var results = ctx.GetNextSequenceValue();

    // Extract the first/single value from the results.
    int? nextSequenceValue = results.Single();

    // Display or utilize the sequence value as needed.
    Console.WriteLine("Next sequence value is: {0}", nextSequenceValue.Value);
}

2. Import the stored procedure into your EDMX model, then invoke it within your Entity Framework context to retrieve the sequence value.

Method 2: Executing Raw SQL Queries

public partial class YourEfContext : DbContext 
{
    .... (other EF stuff) ......

    // Define a method to retrieve the next sequence value.
    public int GetNextSequenceValue()
    {
        var rawQuery = Database.SqlQuery<int>("SELECT NEXT VALUE FOR dbo.TestSequence;");
        var task = rawQuery.SingleAsync();
        int nextVal = task.Result;

        return nextVal;
    }
}

1. Define a method named GetNextSequenceValue within the context class.

// Call the method to obtain the next sequence value.
YourEfContext ctx = new YourEfContext();
int nextSequenceValue = ctx.GetNextSequenceValue();

2. Invoke the method from your code to retrieve the sequence value.

Method 3: Using an Entity Class for Non-Procedure Scenarios

SEQ_TXN_ID txn_id= _context.SEQ_TXN_IDs.SqlQuery("SELECT txn_id_seq.NEXTVAL txn_ID FROM DUAL").FirstOrDefault();

1. Create an entity class to hold the sequence value.

2. Execute raw SQL against the entity class to retrieve the sequence value.

Method 4: Defining a Sequence in Code First Approach

protected override void OnModelCreating( ModelBuilder modelBuilder )
{
    modelBuilder.HasSequence("MySequence");
}

1. Define the sequence using modelBuilder.HasSequence("MySequence") in the OnModelCreating method.

public int GetMySequence()
{
   SqlParameter result = new SqlParameter("@result", System.Data.SqlDbType.Int)
   {
      Direction = System.Data.ParameterDirection.Output
   };

   Database.ExecuteSqlCommand(
              "SELECT @result = (NEXT VALUE FOR MySequence)", result);

   return (int)result.Value;
}

2. Add a method to the context class to retrieve the sequence value.

Method 5: Utilizing an Extension Class for Centralized Sequence Handling

public static class MyDbContextExtensions
{
    public static int NextValueForSequence(this MyDbContext pCtx, Sequence pSequence)
    {
        SqlParameter result = new SqlParameter("@result", System.Data.SqlDbType.Int)
        {
            Direction = System.Data.ParameterDirection.Output
        };
        var sequenceIdentifier = pSequence.GetType()
                    .GetMember(pSequence.ToString())
                    .First()
                    .GetCustomAttribute<DescriptionAttribute>()
                    .Description;
        pCtx.Database.ExecuteSqlCommand($"SELECT @result = (NEXT VALUE FOR [{sequenceIdentifier}]);", result);
        return (int)result.Value;
    }
}

1. Define an extension class with a method to retrieve the sequence value.

ctx.NextValueForSequence(Sequence.OrderNr);

2. Utilize the extension method to obtain the sequence value in your code.

Method 6: Retrieving Sequence Value Using ExecuteScalar (EF Core)

var connection = dbContext.Database.GetDbConnection();
connection.Open();
using (var cmd = connection.CreateCommand())
{
    cmd.CommandText = "SELECT NEXT VALUE FOR ACH.FileIDModifier;";
    var obj = cmd.ExecuteScalar();
    int anInt = (int)obj;
}

1. Obtain a connection to the database.

2. Execute the SQL command using ExecuteScalar to retrieve the sequence value.

Method 7: Ensuring Thread Safety in Asynchronous Scenarios (EF Core)

var rawQuery = dbContext.Database.SqlQuery<Int64>("SELECT NEXT VALUE FOR YOURSEQNAME").FirstOrDefaultAsync();
if(rawQuery != null)
{
    long nextId = await rawQuery;
}

1. Utilize FirstOrDefaultAsync to retrieve the sequence value asynchronously.

2. Handle the result using await to ensure thread safety.

Method 8: Adding a Function to the DbContext for Sequence Retrieval

public async Task<int> NextValueForSequenceAsync(SequenceEnum.Sequence sequence)
{
    SqlParameter result = new SqlParameter("@result", System.Data.SqlDbType.Int)
    {
        Direction = System.Data.ParameterDirection.Output
    };

    var sequenceIdentifier = sequence.GetType().GetMember(sequence.ToString()).First().GetCustomAttribute<DescriptionAttribute>().Description;

    await Database.ExecuteSqlRawAsync($"SELECT @result = (NEXT VALUE FOR [{sequenceIdentifier}])", result);

    return (int)result.Value;
}

1. Add a method to the DbContext class to asynchronously retrieve the sequence value.

await context.NextValueForSequenceAsync(SequenceEnum.Sequence.FirstSequence);

2. Invoke the method asynchronously in your code.

Method 9: Generating SELECT Statements for Sequence Values (EF Core)

public async Task<int> GetNextValueAsync(string sequenceName, string? schema = null)
{
    var sqlGenerator = this.GetService<IUpdateSqlGenerator>();
    var sql = sqlGenerator.GenerateNextSequenceValueOperation(sequenceName, schema);

    var result = await Database.SqlQueryRaw<int>(sql).ToListAsync();
    return result.Single();
}

1. Define a method in the DbContext class to generate SELECT statements for retrieving sequence values.

var nextValue = await context.GetNextValueAsync("MySequence");

2. Invoke the method to retrieve the sequence value using the generated SQL statement.

These methods provide different approaches for obtaining the next value from a SQL Server sequence using Entity Framework. Select the one that suits your project's needs and preferences.