C# MySQL/实体框架-错误'；列'的值；RelationshipDetails中的fk列为DBNull'；在生成模型时发生

我正在尝试将MySql 5.1与Entity Framework 6.0和DbContext generator 5.0、.Net Framework 4.0、Visual Studio 2010和C#一起使用。我已经从NuGet下载了最新的软件包。我能够将表从数据库添加到模型中，在某种程度上没有问题（我很难确定）。在该点之后，尝试添加新表或甚至生成现有模型会出现如下错误：

Unable to generate the model because of the following exception: 'The value for column 'FkColumn' in table 'RelationshipDetails' is DBNull.
Unable to cast object of type 'System.DBNull' to type 'System.String'.

我已尝试在.tt文件中启用调试，但在加载和解析.tt文件之前会发生异常。我也尝试过删除表，但当我尝试从数据库上载新表或尝试保存现有文件时，错误仍然会发生。奇怪的是，tt模板确实会被调用，并生成类。但它不会从数据库中加载任何新表。在模板上运行调试器时，会收到以下消息：

Error   2   An Exception was thrown while running the transformation code. The process cannot continue.  The following Exception was thrown:
System.Runtime.Remoting.RemotingException: Object '/9747a151_8703_4922_90da_93472afe62d2/fjgxduxp4yb2qwls+ipl7t98_89.rem' has been disconnected or does not exist at the server.
   at Microsoft.VisualStudio.TextTemplating.TransformationRunner.get_Errors()
   at Microsoft.VisualStudio.TextTemplating.Engine.CompileAndRunCode(String generatorCode, ITextTemplatingEngineHost host, TemplateProcessingSession session)       C:\Development\CCBPlus\CCB Server\Model\CCBPlus.tt  0   0   

有人对如何进行这项工作有什么建议吗？我现在处于停顿状态，已经删除并重新创建了3次我的模型，但还没有进一步弄清楚是什么原因造成了这种情况

谢谢，尼尔

更多的研究似乎表明，一旦定义了名为Contact的实体，添加链接到该实体的任何其他实体都会导致错误。我可以添加其他未链接到联系人的实体，不会出现问题。联系人实体的定义如下：

     <EntityType Name="Contact">
      <Key>
        <PropertyRef Name="ContactId" />
      </Key>
      <Property Type="Int32" Name="ContactId" Nullable="false" annotation:StoreGeneratedPattern="Identity" />
      <Property Type="Byte" Name="ContactType" Nullable="false" />
      <Property Type="String" Name="DisplayName" Nullable="false" MaxLength="80" FixedLength="false" Unicode="false" />
      <Property Type="String" Name="SearchName" Nullable="false" MaxLength="80" FixedLength="false" Unicode="false" />
      <Property Type="String" Name="Prefix" MaxLength="15" FixedLength="false" Unicode="false" />
      <Property Type="String" Name="LastName" MaxLength="50" FixedLength="false" Unicode="false" />
      <Property Type="String" Name="Initials" MaxLength="10" FixedLength="false" Unicode="false" />
      <Property Type="String" Name="FirstName" MaxLength="40" FixedLength="false" Unicode="false" />
      <Property Type="String" Name="Suffix" MaxLength="10" FixedLength="false" Unicode="false" />
      <Property Type="String" Name="OrganizationName" MaxLength="50" FixedLength="false" Unicode="false" />
      <Property Type="String" Name="InCareOf" MaxLength="80" FixedLength="false" Unicode="false" />
      <Property Type="DateTime" Name="Birthdate" />
      <Property Type="DateTime" Name="Deceased" />
      <Property Type="String" Name="SocialSecurityNumber" MaxLength="20" FixedLength="false" Unicode="false" />
      <Property Type="SByte" Name="Gender" />
      <Property Type="String" Name="CulturePreference" MaxLength="10" FixedLength="false" Unicode="false" />
      <Property Type="DateTime" Name="LastMeeting" />
      <Property Type="String" Name="Hobbies" MaxLength="100" FixedLength="false" Unicode="false" />
      <Property Type="String" Name="Notes" MaxLength="1073741823" FixedLength="false" Unicode="false" />
      <Property Type="Boolean" Name="Inactive" Nullable="false" />
      <Property Type="DateTime" Name="Created" Nullable="false" />
      <Property Type="DateTime" Name="LastModified" Nullable="false" />
      <NavigationProperty Name="AccountHolders" Relationship="CCB.EntityModel.fk_AccountHolder_Contact" FromRole="Contact" ToRole="AccountHolder" />
      <NavigationProperty Name="Branches" Relationship="CCB.EntityModel.fk_Branch_ContactInfo" FromRole="Contact" ToRole="Branch" />
      <NavigationProperty Name="Company" Relationship="CCB.EntityModel.fk_Company_ContactInfo" FromRole="Contact" ToRole="Company" />
      <NavigationProperty Name="ContactCategories" Relationship="CCB.EntityModel.fk_ContactCategory_Contact" FromRole="Contact" ToRole="ContactCategory" />
      <NavigationProperty Name="ContactCommunications" Relationship="CCB.EntityModel.fk_ContactCommunication_Contact" FromRole="Contact" ToRole="ContactCommunication" />
      <NavigationProperty Name="Agents" Relationship="CCB.EntityModel.fk_Agent_ContactInfo" FromRole="Contact" ToRole="Agent" />
    </EntityType>
    <Association Name="fk_AccountHolder_Contact">
      <End Type="CCB.EntityModel.Contact" Role="Contact" Multiplicity="1" />
      <End Type="CCB.EntityModel.AccountHolder" Role="AccountHolder" Multiplicity="*" />
      <ReferentialConstraint>
        <Principal Role="Contact">
          <PropertyRef Name="ContactId" />
        </Principal>
        <Dependent Role="AccountHolder">
          <PropertyRef Name="ContactId" />
        </Dependent>
      </ReferentialConstraint>
    </Association>
    <Association Name="fk_Branch_ContactInfo">
      <End Type="CCB.EntityModel.Contact" Role="Contact" Multiplicity="1" />
      <End Type="CCB.EntityModel.Branch" Role="Branch" Multiplicity="*" />
    </Association>
    <Association Name="fk_Company_ContactInfo">
      <End Type="CCB.EntityModel.Contact" Role="Contact" Multiplicity="1" />
      <End Type="CCB.EntityModel.Company" Role="Company" Multiplicity="0..1" />
      <ReferentialConstraint>
        <Principal Role="Contact">
          <PropertyRef Name="ContactId" />
        </Principal>
        <Dependent Role="Company">
          <PropertyRef Name="CompanyContactId" />
        </Dependent>
      </ReferentialConstraint>
    </Association>
    <Association Name="fk_ContactCategory_Contact">
      <End Type="CCB.EntityModel.Contact" Role="Contact" Multiplicity="1" />
      <End Type="CCB.EntityModel.ContactCategory" Role="ContactCategory" Multiplicity="*" />
      <ReferentialConstraint>
        <Principal Role="Contact">
          <PropertyRef Name="ContactId" />
        </Principal>
        <Dependent Role="ContactCategory">
          <PropertyRef Name="ContactId" />
        </Dependent>
      </ReferentialConstraint>
    </Association>
    <Association Name="fk_ContactCommunication_Contact">
      <End Type="CCB.EntityModel.Contact" Role="Contact" Multiplicity="1" />
      <End Type="CCB.EntityModel.ContactCommunication" Role="ContactCommunication" Multiplicity="*" />
    </Association>

---

我最终删除了数据库并从MySQL工作台模型中重新创建了它，问题就消失了。很明显，MySQL中的某些内容由于模型的重复上传而损坏。但是，根据模型重新创建会产生另一个问题，如所述。当你使用开源时，乐趣永远不会停止

CREATE TABLE `Contacts` (
   `ContactId` int(11) NOT NULL,
   `ContactType` bit(3) NOT NULL COMMENT 'Contact Type: 0=Individual, 1=Corporate, 2=Family, 3=Branch, 4=Department, 5=Group, 6=Fund/GIC/Bank company',
   `DisplayName` varchar(80) NOT NULL,
   `SearchName` varchar(80) NOT NULL,
   `Prefix` varchar(15) DEFAULT NULL,
   `LastName` varchar(50) DEFAULT NULL,
   `Initials` varchar(10) DEFAULT NULL,
   `FirstName` varchar(40) DEFAULT NULL,
   `Suffix` varchar(10) DEFAULT NULL,
   `OrganizationName` varchar(50) DEFAULT NULL,
   `InCareOf` varchar(80) DEFAULT NULL COMMENT 'If mail is to be sent with the line "In care of [X]"',
   `Birthdate` datetime DEFAULT NULL,
   `Deceased` datetime DEFAULT NULL,
   `SocialSecurityNumber` varchar(20) DEFAULT NULL,
   `Gender` bit(1) DEFAULT b'0' COMMENT '0=Male,1=Female',
   `CulturePreference` varchar(10) DEFAULT 'EN-CA' COMMENT 'Global Culture variable, e.g. EN-CA or FR-CA or other.',
   `LastMeeting` datetime DEFAULT NULL,
   `Hobbies` varchar(100) DEFAULT NULL,
   `Inactive` tinyint(1) NOT NULL DEFAULT '0',
   `Created` datetime NOT NULL,
   `LastModified` datetime NOT NULL,
   PRIMARY KEY (`ContactId`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='Stores contact and optionally personal information';