Loss of Precision from C# to SQL Server

Question

This is an issue I am facing which is causing loss of precision when storing in SQL Server database from C# Entity Framework.

1. SQL Server Data Type is decimal(20, 15)
2. In C# Property is defined as public decimal AssignedGrossBudget { get; set; }
3. in C# value in variable (AssignedGrossBudget) is 34.09090909090909
4. But in SQL Server table it is 34.090000000000000

What could be wrong? (I am using Entity Framework db.SaveChanges(); and SQLBulkCopy to store data from c# to SQL Server)

I want to store 34.09090909090909 instead of 34.090000000000000.

I checked by directly inserting in the table and it works.

Answer 1

A simple example shows that no such loss of precision occurs with correctly written code:

    static void Main(string[] args)
    {
        decimal d = 34.09090909090909M;
        Console.WriteLine(d);

        SqlConnectionStringBuilder scsb = new SqlConnectionStringBuilder();
        scsb.IntegratedSecurity = true;
        scsb.DataSource = @".\sql2012";

        using (SqlConnection conn = new SqlConnection(scsb.ConnectionString)) {
            conn.Open();

            using (SqlCommand cmd = new SqlCommand(
               "select cast(@d as DECIMAL(20,15))", conn))
            {
                cmd.Parameters.AddWithValue("@d", d);
                decimal rd = (decimal) cmd.ExecuteScalar();
                Console.WriteLine(rd);
            }
        }
    }

Therefore I must conclude the problem is with your code, which is not posted.

Answer 2

Thanks Urril and Remus.

I make changes in Entity Framework as below:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity<StationMapping>().Property(x => x.AssignedGrossBudget).HasPrecision(35, 15);

        }

And for SQL BulkCopy I added Data Type as per Remus suggestion.

SpotLookupTable.Columns.Add(new DataColumn("GrossBudget",typeof(decimal)));

Its is working now and there is no loss (or Negligible).

Cheers