EF中对decimal类型在实体属性中的精度控制

EF中对decimal类型在实体属性中的精度控制

EF中对decimal类型数据进行存储时，对多位小数默认会截断取2位保存，但一些高精度场合不能满足要求，则需要我们对其改造一下：
1、新建DecimalPrecisionAttribute.cs，最好和上下文在同一个命名空间内，以减少引用

```csharp
using System;
using System.Collections.Generic;
using System.Data.Entity.ModelConfiguration.Configuration;
using System.Data.Entity.ModelConfiguration.Conventions;
using System.Linq;
using System.Web;

namespace AppBoxMvc.Models
{
    /// <summary>
    /// 精度属性控制
    /// </summary>
    [AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = false)]
    public sealed class DecimalPrecisionAttribute : Attribute
    {
        #region Field
         private byte _precision = 18;
         public byte _scale = 4;
         #endregion
 
         #region Construct
         /// <summary>
         /// <para>自定义Decimal类型的精确度属性</para>
         /// </summary>
         /// <param name="precision">precision
         /// <para>精度（默认18）</para></param>
         /// <param name="scale">scale
         /// <para>小数位数（默认4）</para></param>
         public DecimalPrecisionAttribute(byte precision = 18, byte scale = 4)
         {
             Precision = precision;
             Scale = scale;
         } 
         #endregion
         
         #region Property
         /// <summary>
         /// 精确度（默认18）
         /// </summary>
         public byte Precision
         {
             get { return this._precision; }
             set { this._precision = value; }
         }
 
         /// <summary>
         /// 保留位数（默认4）
         /// </summary>
         public byte Scale
         {
             get { return this._scale; }
             set { this._scale = value; }
         } 
         #endregion
     }
 
     /// <summary>
     /// 用于modelBuilder全局设置自定义精度属性
     /// </summary>
     public class DecimalPrecisionAttributeConvention
         : PrimitivePropertyAttributeConfigurationConvention<DecimalPrecisionAttribute>
     {
         public override void Apply(ConventionPrimitivePropertyConfiguration configuration, DecimalPrecisionAttribute attribute)
         {
             if (attribute.Precision < 1 || attribute.Precision > 38)
             {
                 throw new InvalidOperationException("Precision must be between 1 and 38.");
             }
             if (attribute.Scale > attribute.Precision)
             {
                 throw new InvalidOperationException("Scale must be between 0 and the Precision value.");
             }
             configuration.HasPrecision(attribute.Precision, attribute.Scale);
         }

    }
}

2、OnModelCreating新增属性

```csharp
protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();//移除复数表名的契约
            modelBuilder.Conventions.Remove<IncludeMetadataConvention>();//防止黑幕交易 要不然每次都要访问
            modelBuilder.HasDefaultSchema("SCM");
            //base.OnModelCreating(modelBuilder);
            //注册函数
            modelBuilder.Conventions.Add(new FunctionsConvention("SCM", this.GetType()));
            modelBuilder.Conventions.Add(new DecimalPrecisionAttributeConvention());
}

注意，在NFineFramework架构中数据库方法中可能调用某个上下文，如JobAppDbContext : DbContext，则只需要在该文属性中增加一个注册即可：
modelBuilder.Conventions.Add(new DecimalPrecisionAttributeConvention());//注册Decimal精度函数

```csharp
    public class JobAppDbContext : DbContext
    {
        public JobAppDbContext()
            : base("JobAppDbContext")
        {
            this.Configuration.AutoDetectChangesEnabled = false;
            this.Configuration.ValidateOnSaveEnabled = false;
            this.Configuration.LazyLoadingEnabled = false;
            this.Configuration.ProxyCreationEnabled = false;
        }
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            string assembleFileName = Assembly.GetExecutingAssembly().CodeBase.Replace("JobApp.Data.DLL", "JobApp.Mapping.DLL").Replace("file:///", "");
            Assembly asm = Assembly.LoadFile(assembleFileName);
            var typesToRegister = asm.GetTypes()
            .Where(type => !String.IsNullOrEmpty(type.Namespace))
            .Where(type => type.BaseType != null && type.BaseType.IsGenericType && type.BaseType.GetGenericTypeDefinition() == typeof(EntityTypeConfiguration<>));
            foreach (var type in typesToRegister)
            {
                dynamic configurationInstance = Activator.CreateInstance(type);
                modelBuilder.Configurations.Add(configurationInstance);
                modelBuilder.Conventions.Add(new DecimalPrecisionAttributeConvention());//注册Decimal精度函数
            }
            base.OnModelCreating(modelBuilder);
        }
    }

3、实体属性绑定

```csharp
.....
 		[DecimalPrecision(19, 4)]
        public decimal T_SCM_QUTV_BASIC_PRICE { get; set; }//购买价格

        [Display(Name = "税后价格")]
        [DecimalPrecision(19, 4)]
        public decimal T_SCM_QUTV_END_PRICE { get; set; }//税后价格
........

参考博文：https://www.cnblogs.com/su1643/p/10982197.html