blocks|key|541964|text|只支持标量类型、字符串和byte[]。可用的最大标量类型是十进制。其中“只”允许28-29位有效数字。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|541965|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Only scalar types, string, and byte[] are supported.
The largest scalar type available is decimal. Which "only" allows 28-29 significant digits.

blocks|key|541972|text|实体框架必须对如何存储这些信息做出假设。例如，如果您使用的是server，则bigint无法工作，因为您的值可能比使用bigint的值更大或更小。varchar会更合适吗？有可能，但如果你真的想让它是一个数字，而不是一个标识符，那么让EF将其作为一个数字进行查询将是有问题的。因此，在本质上，有一些不那么含糊的类型，比如long或string，在这些类型中，您不会对如何将其存储到实体框架中留下猜测。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|541973|entityMap^0|12|6|1N|6|21|7|4G|4|4L|6|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|G|$]]

Entity Framework would have to make assumptions about how to store that. If you're using SQL server, for example, <code>bigint</code> doesn't work because your values could be larger or smaller than what's possible with <code>bigint</code>. Would <code>varchar</code> be more appropriate? Possibly, but if you truly mean it to be a number and not say, an identifier, asking EF to query that as a number is going to be problematic. So essentially, there are less ambiguous types like <code>long</code> or <code>string</code> where you're not leaving the guesswork on how to store it up to Entity Framework.

blocks|key|1556102|text|由于EFCore2.1，当您在您的值转换类的OnModelCreating()函数中定义数据模型时，可以定义DbContext。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1556103|最棒的是，这允许在从数据库读取或写入数据库时自动转换属性值！|BOLD|1556104|因此，在您的示例中，您有一个BigInteger属性(Reputation)在C#中，而在MySQL中有一个相应的INT(25)字段，您可以这样做：|1556105|var+converter+=+new+ValueConverter<BigInteger,+long>(++++
++++model+=>+(long)model,
++++provider+=>+new+BigInteger(provider));

modelBuilder
++++.Entity<AllianceRank>()
++++.Property(e+=>+e.Reputation)
++++.HasConversion(converter);|code-block|syntax|javascript|1556106|实际上，您可能需要使用可变长度的string类型(如VARBINARY)来存储MySQL而不是INT(25)中的值，因为C#+BigInteger存储的值要大得多，因此在转换为INT(25)或C#+long时会导致异常。|1556107|entityMap|0|LINK|mutability|MUTABLE|url|https://learn.microsoft.com/en-us/ef/core/modeling/value-conversions^0|M|H|1I|9|H|3|0|0|Q|3|0|E|A|R|A|1L|7|0|0|G|6|1B|7|1R|A|2G|7|2R|4|0^^$0|@$1|2|3|4|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]]|D|@$9|14|A|15|1|16]]|E|$]]|$1|F|3|G|5|6|7|17|8|@$9|18|A|19|B|H]]|D|@]|E|$]]|$1|I|3|J|5|6|7|1A|8|@$9|1B|A|1C|B|C]|$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|K|3|L|5|M|7|1H|8|@]|D|@]|E|$N|O]]|$1|P|3|Q|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]|$9|1N|A|1O|B|C]|$9|1P|A|1Q|B|C]|$9|1R|A|1S|B|C]]|D|@]|E|$]]|$1|R|3|-4|5|6|7|1T|8|@]|D|@]|E|$]]]|S|$T|$5|U|V|W|E|$X|Y]]]]

Since EF Core 2.1, you can define <a href="https://learn.microsoft.com/en-us/ef/core/modeling/value-conversions" rel="nofollow noreferrer">Value Conversions</a> when you define data models in the <code>OnModelCreating()</code> function of your <code>DbContext</code> class. 

The best part is that this allows property values to be converted automatically when reading from or writing to the database!

So, in your case, you have a <code>BigInteger</code> property (<code>Reputation</code>) in C# and a corresponding <code>INT(25)</code> field in MySQL, you can do this:

<pre><code>var converter = new ValueConverter&lt;BigInteger, long&gt;( 
 model =&gt; (long)model,
 provider =&gt; new BigInteger(provider));

modelBuilder
 .Entity&lt;AllianceRank&gt;()
 .Property(e =&gt; e.Reputation)
 .HasConversion(converter);
</code></pre>

P.S. You might actually wanna use a variable-length <code>string</code> type (like VARBINARY) to store the value in MySQL instead of <code>INT(25)</code>, as a C# <code>BigInteger</code> store a much larger value and therefore cause exceptions while converting to <code>INT(25)</code> or C# <code>long</code>.

blocks|key|1556154|text|使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1556155|public+long+FieldName+{+get;+set;+}|code-block|syntax|javascript|1556156|在模型类中，它将是SQL中的bigint数据类型|offset|length|style|CODE|1556157|entityMap^0|0|0|E|6|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Use
<pre><code>public long FieldName { get; set; }
</code></pre>
In your Model class, it will be <code>bigint</code> datatype in SQL

blocks|key|1753552|text|对于那些在类似情况下收到这一神秘错误信息的可怜灵魂来说：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1753553|无法将“System.Int64”类型的对象强制转换为“System.Decimal”类型。|1753554|您将假设实体框架将自动将Server+bigint+(64位无符号整数)映射到适当的C#+long+(也是64位无符号整数)，但是.|1753555|因此，您必须在使用HasColumnType()，的OnModelCreating(ModelBuilder+modelbuilder)方法中提供一些指导，如下所示：|offset|length|style|BOLD|1753556|using+Microsoft.EntityFrameworkCore;

namespace+Some.Namespace
{
++++public+class+YourClassDbContext+:+DbContext
++++{
++++++++public+YourClassDbContext(DbContextOptions<YourClassDbContext>+options)+:+base(options)+
++++++++{
++++++++}

++++++++public+YourClassDbContext()+{}

++++++++protected+override+void+OnModelCreating(ModelBuilder+modelBuilder)
++++++++{
++++++++++++/*+omitted+stuff+for+PK+and+index+*/
++++++++++++modelBuilder.Entity<ClassXYZ>().Property(t+=>+t.Id).HasColumnType("long");
++++++++++++
++++++++++++base.OnModelCreating(modelBuilder);
++++++++}|code-block|syntax|javascript|1753557|非常感谢上面的@Kelvin莱，他的回答使我走上了正确的道路，并感谢https://learn.microsoft.com/en-us/ef/core/modeling/value-conversions|1753558|entityMap|0|LINK|mutability|MUTABLE|url|https://learn.microsoft.com/en-us/ef/core/modeling/value-conversions^0|0|0|0|9|F|0|0|Y|1W|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|13|8|@$H|14|I|15|J|K]]|9|@]|A|$]]|$1|L|3|M|5|N|7|16|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|17|8|@]|9|@$H|18|I|19|1|1A]]|A|$]]|$1|S|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

For the poor souls who receive this cryptic error message in a similar situation:
Unable to cast object of type 'System.Int64' to type 'System.Decimal'.
You would assume that Entity Framework would automatically map a SQL Server bigint (64 bit unsigned integer) to the appropriate C# long (also 64 bit unsigned integer), but noo...
So, you have to provide a bit of guidance, in the OnModelCreating(ModelBuilder modelbuilder) method of your DbContext, using HasColumnType(), like so:
<pre><code>using Microsoft.EntityFrameworkCore;

namespace Some.Namespace
{
 public class YourClassDbContext : DbContext
 {
 public YourClassDbContext(DbContextOptions&lt;YourClassDbContext&gt; options) : base(options) 
 {
 }

 public YourClassDbContext() {}

 protected override void OnModelCreating(ModelBuilder modelBuilder)
 {
 /* omitted stuff for PK and index */
 modelBuilder.Entity&lt;ClassXYZ&gt;().Property(t =&gt; t.Id).HasColumnType(&quot;long&quot;);
 
 base.OnModelCreating(modelBuilder);
 }
 
</code></pre>
With many thanks to @Kelvin Lai above, whose answer put me on the right path, and <a href="https://learn.microsoft.com/en-us/ef/core/modeling/value-conversions" rel="nofollow noreferrer">https://learn.microsoft.com/en-us/ef/core/modeling/value-conversions</a>

blocks|key|1753560|text|我的问题解决了:使用int64而不是biginteger|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1753561|public+class+MyClassName
++++{
++++++++[Key]
++++++++public+Int64+TableId+{+get;+set;+}
++++}|code-block|syntax|javascript|1753562|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

my problem solved by :
by use int64 instead of biginteger
<pre><code>public class MyClassName
 {
 [Key]
 public Int64 TableId { get; set; }
 }
</code></pre>

I am needing to use the <code>BigInteger</code> class to handle large integers to my classes, however when trying to use EntityFramework Core to map to a DB table I recieve the following error:

<blockquote>
 The property <code>AllianceRank.Reputation</code> could not be mapped, because
 it is of type <code>BigInteger</code> which is not a supported
 primitive type or a valid entity type. Either explicitly map this
 property, or ignore it.
</blockquote>

<pre><code>[Column("reputation")]
public BigInteger Reputation { get; set; }
</code></pre>

It would seem that <code>BigIntegers</code> are not a supported type for mapping. How can I force it to map, or otherwise resolve this issue?

Entity Framework Core will not map to BigInteger

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我需要使用BigInteger类来处理类的大整数，但是当试图使用EntityFramework Core映射到DB表时，我会收到以下错误：属性AllianceRank.Reputation无法映射，因为它的类型是BigInteger，它不是受支持的原始类型或有效的实体类型。显式映射此属性，或忽略它。[Column("r...

问实体框架核心不会映射到BigInteger
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