【.NET】设置EntityFramework中decimal类型数据精度 [转]

[转]https://blog.csdn.net/u013938578/article/details/78740152

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);
}
}