Best Data annotation for a Decimal(18,2)

Question

I have a column inside my sql server 2008 wih type of Decimal(18,2). But on entity framework what is the best data annotation validation I can apply to this pro

Answer 1

If you write the 'column' annotation, will work fine

    [Required]
    [Column(TypeName = "decimal(18, 6)")]
    public decimal Foo { get; set; }

Answer 2

 [Range(1,(double) decimal.MaxValue, ErrorMessage="value should be between{1} and {2}."]

Answer 3

There is no explicit data annotation for a decimal so you need to use two separate ones to add constraints.

Two Decimal Points

[RegularExpression(@"^\d+\.\d{0,2}$")]

This regular expression will make sure that the property has at most two decimal places.

Max 18 digits

[Range(0, 9999999999999999.99)]

Assuming you aren't accepting any negative numbers. Otherwise, replace 0 with -9999999999999999.99.

Result

[RegularExpression(@"^\d+\.\d{0,2}$")]
[Range(0, 9999999999999999.99)]
public decimal Property { get; set; }

Answer 4

For a different approach which some may consider more readable, you can override the OnModelCreating method of your DbContext to set precision, like so:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {

           modelBuilder.Entity<YourEntity>()
                    .Property(x => x.TheProprty)
                    .HasPrecision(18, 2);
    }

Advantage: strongly typed vs custom regular expression

Disadvantage: can't see it on the class with just a scan

Answer 5

This seems to be the correct answer ( the above answers either restrict valid numbers that can be inserted into a data type of Decimal(18,2) or cause compile errors if you apply them to your code -- please confirm for yourself):

Use the following two constraints together:

Two Decimal Points

[RegularExpression(@"^\d+.?\d{0,2}$", ErrorMessage = "Invalid Target Price; Maximum Two Decimal Points.")]

Max 18 digits

  [Range(0, 9999999999999999.99, ErrorMessage = "Invalid Target Price; Max 18 digits")]

Answer 6

Following on from @Schmalls example (and comment re building it into an attribute) I've created a working example (uses C# 6 string interpolation):

public class PrecisionAndScaleAttribute : RegularExpressionAttribute
{
    public PrecisionAndScaleAttribute(int precision, int scale) : base($@"^(0|-?\d{{0,{precision - scale}}}(\.\d{{0,{scale}}})?)$")
    {

    }
}

Usage:

[PrecisionAndScale(6, 2, ErrorMessage = "Total Cost must not exceed $9999.99")]
public decimal TotalCost { get; set; }