设置EntityFramework中decimal类型数据精度

EF中默认的decimal数据精度为两位数，当我们数据库设置的精度大于2时，EF将只会保留到2为精度。

e.g.  2.1999将会被保存为2.20

网上找到常见的方法为重写DbContext的OnModelCreating方法：

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
　　modelBuilder.Entity<Product>().Property(x => x.Price).HasPrecision(18, 4);
}

但如果数据表多或者Decimal类型字段多的话，用OnModelCreating的方法将会变得相当冗余，而且不便管理。

我推荐使用Attribute属性标签进行设置，在Entity Model class中decimal的字段上方直接添加自定义拓展的属性标签即可。

e.g.

其中 [DecimalPrecision(18, 4)]即是我们自定义的精度Attribute

具体实现代码如下：

 1     /// <summary>
 2     /// <para>自定义Decimal类型的精度属性</para>
 3     /// </summary>
 4     [AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = false)]
 5     public sealed class DecimalPrecisionAttribute : Attribute
 6     {
 7
 8         #region Field
 9         private byte _precision = 18;
10         public byte _scale = 4;
11         #endregion
12
13         #region Construct
14         /// <summary>
15         /// <para>自定义Decimal类型的精确度属性</para>
16         /// </summary>
17         /// <param name="precision">precision
18         /// <para>精度（默认18）</para></param>
19         /// <param name="scale">scale
20         /// <para>小数位数（默认4）</para></param>
21         public DecimalPrecisionAttribute(byte precision = 18, byte scale = 4)
22         {
23             Precision = precision;
24             Scale = scale;
25         }
26         #endregion
27
28         #region Property
29         /// <summary>
30         /// 精确度（默认18）
31         /// </summary>
32         public byte Precision
33         {
34             get { return this._precision; }
35             set { this._precision = value; }
36         }
37
38         /// <summary>
39         /// 保留位数（默认4）
40         /// </summary>
41         public byte Scale
42         {
43             get { return this._scale; }
44             set { this._scale = value; }
45         }
46         #endregion
47     }
48
49     /// <summary>
50     /// 用于modelBuilder全局设置自定义精度属性
51     /// </summary>
52     public class DecimalPrecisionAttributeConvention
53         : PrimitivePropertyAttributeConfigurationConvention<DecimalPrecisionAttribute>
54     {
55         public override void Apply(ConventionPrimitivePropertyConfiguration configuration, DecimalPrecisionAttribute attribute)
56         {
57             if (attribute.Precision < 1 || attribute.Precision > 38)
58             {
59                 throw new InvalidOperationException("Precision must be between 1 and 38.");
60             }
61             if (attribute.Scale > attribute.Precision)
62             {
63                 throw new InvalidOperationException("Scale must be between 0 and the Precision value.");
64             }
65             configuration.HasPrecision(attribute.Precision, attribute.Scale);
66         }
67     }

再在DbContext重写OnModelCreating，添加自定义的DecimalPrecisionAttributeConvention即可以方便地任意添加需要精度控制的字段。

    public class Project_DbContext : DbContext
    {
        public Project_DbContext() : base("DefaultConnection") { }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Conventions.Add(new DecimalPrecisionAttributeConvention());
            base.OnModelCreating(modelBuilder);
        }

    }