【.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：

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

1.   public class Project_DbContext : DbContext
2.   {
3.   public Project_DbContext() : base("DefaultConnection") { }
4.    
5.   protected override void OnModelCreating(DbModelBuilder modelBuilder)
6.   {
7.   modelBuilder.Conventions.Add(new DecimalPrecisionAttributeConvention());
8.   base.OnModelCreating(modelBuilder);
9.   }
10.    
11.   }

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：

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

1.   public class Project_DbContext : DbContext
2.   {
3.   public Project_DbContext() : base("DefaultConnection") { }
4.    
5.   protected override void OnModelCreating(DbModelBuilder modelBuilder)
6.   {
7.   modelBuilder.Conventions.Add(new DecimalPrecisionAttributeConvention());
8.   base.OnModelCreating(modelBuilder);
9.   }
10.    
11.   }