为什么在unity编译器中,会报错呢?错误:Assets/unityMySql.cs(3,14): error CS0234: The type or namespace name `Data' does not exist in the namespace `System'. Are you missing an assembly reference?。当我把system.Data.dll加入到Plugins文件夹中时 ,上面错误没有了,但是又出现了新的错误:Unhandled Exception: Mono.CSharp.InternalErrorException: Assets/SqlAccess.cs(10,14): SqlAccess ---> Mono.CSharp.InternalErrorException: Assets/SqlAccess.cs(12,35): SqlAccess.dbConnection ---> System.IO.FileNotFoundException: Could not load file or assembly 'System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies.File name: 'System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' at (wrapper managed-to-native) System.MonoCustomAttrs:GetCustomAttributesInternal (System.Reflection.ICustomAttributeProvider,System.Type,bool) at System.MonoCustomAttrs.GetCustomAttributesBase (ICustomAttributeProvider obj, System.Type attributeType) [0x00000] in <filename unknown>:0 at System.MonoCustomAttrs.GetCustomAttributes (ICustomAttributeProvider obj, System.Type attributeType, Boolean inherit) [0x00000] in <filename unknown>:0 at System.MonoType.GetCustomAttributes (System.Type attributeType, Boolean inherit) [0x00000] in <filename unknown>:0