1. Pomelo.EntityFrameworkCore.MySql不是.net core 3.0会报如下错:

Method ‘get_Info’ in type ‘Pomelo.EntityFrameworkCore.MySql.Infrastructure.Internal.MySqlOptionsExtension’ from assembly ‘Pomelo.EntityFrameworkCore.MySql, Version=2.2.0.0, Culture=neutral, PublicKeyToken=null’ does not have an implementation.

只能去安装对应的3.0包了，然而在今天(2019年11月12日)的时候，Nuget管理工具里最高的发布版本是2.2.6,那就装个RC版的吧。要注意的是，它的官方文档上说了，这个命令只支持VS2017+并且Nuget是V4.3以上的版本才行。命令如下：

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Install-Package Pomelo.EntityFrameworkCore.MySql -Version 3.0.0-rc2.final
  1. .net core 3.0将ef工具抽出去了。

MySQL包装完之后，执行命令，又崩了。错误如下：

dotnet ef
dotnet : 无法执行，因为找不到指定的命令或文件。
所在位置 行:1 字符: 1

官网是这么解释的，也提供了相应的解决办法，那么就执行全局工具安装脚本吧。问题解决。

New behavior

Starting in 3.0, the .NET SDK does not include the dotnet ef tool, so before you can use it you have to explicitly install it as a local or global tool.

Why

This change allows us to distribute and update dotnet ef as a regular .NET CLI tool on NuGet, consistent with the fact that the EF Core 3.0 is also always distributed as a NuGet package.

Mitigations

To be able to manage migrations or scaffold a DbContext, install dotnet-ef as a global tool:

consoleCopy

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>$ dotnet tool install --global dotnet-ef
>

You can also obtain it a local tool when you restore the dependencies of a project that declares it as a tooling dependency using a tool manifest file.

  1. MySQL本身的错误。

    哗啦啦一堆脚本执行，没问题，最后咔，出错了。

MySql.Data.MySqlClient.MySqlException (0x80004005): Specified key was too long; max key length is 767 bytes
—> MySql.Data.MySqlClient.MySqlException (0x80004005): Specified key was too long; max key length is 767 bytes
at MySqlConnector.Core.ResultSet.ReadResultSetHeaderAsync(IOBehavior ioBehavior) in C:\projects\mysqlconnector\src\MySqlConnector\Core\ResultSet.cs:line 49
at MySql.Data.MySqlClient.MySqlDataReader.ActivateResultSet() in C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlDataReader.cs:line 130
at MySql.Data.MySqlClient.MySqlDataReader.CreateAsync(CommandListPosition commandListPosition, ICommandPayloadCreator payloadCreator, IDictionary2 cachedProcedures, IMySqlCommand command, CommandBehavior behavior, IOBehavior ioBehavior, CancellationToken cancellationToken) in C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlDataReader.cs:line 391 at MySqlConnector.Core.CommandExecutor.ExecuteReaderAsync(IReadOnlyList1 commands, ICommandPayloadCreator payloadCreator, CommandBehavior behavior, IOBehavior ioBehavior, CancellationToken cancellationToken) in C:\projects\mysqlconnector\src\MySqlConnector\Core\CommandExecutor.cs:line 62