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POAutoMapper.AutoMapperMappingException: Type 'System.String' does not have a default constructor
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  1. POAutoMapper.AutoMapperMappingException: Type 'System.String' does not have a default constructor
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    copied!<p>A strange error began occurring in our code in the lest week or two. I am trying to identify the root cause of the mapping failure. The most-inner exception itself is puzzling: <code>Type 'System.String' does not have a default constructor</code></p> <p><strong>I don't understand what the exception is telling me. Can you explain what has happened and maybe how I could resolve this bug?</strong></p> <p>The mapper is used within a generic method:</p> <pre><code>public TEntity UpdateWithHistory&lt;TEntity&gt;(TEntity entity, int? entityID, int? interviewID) where TEntity : class { var snapshot = _interviewContext.Find&lt;TEntity&gt;(entityID); // This is call that fails var history = Mapper.Map&lt;TEntity, TEntity&gt;(snapshot); _interviewHistory.Set&lt;TEntity&gt;().Add(history); MarkModified(entity); return Mapper.Map(entity, snapshot); } </code></pre> <p>In the above code, snapshot is NOT null. The full exception:</p> <pre><code>AutoMapper.AutoMapperMappingException: Trying to map Recog.Web.Models.InterviewComment to Recog.Web.Models.InterviewComment. Using mapping configuration for Recog.Web.Models.InterviewComment to Recog.Web.Models.InterviewComment Exception of type 'AutoMapper.AutoMapperMappingException' was thrown. ---&gt; AutoMapper.AutoMapperMappingException: Trying to map System.String to System.String. Using mapping configuration for System.String to System.String Destination property: Comment Exception of type 'AutoMapper.AutoMapperMappingException' was thrown. ---&gt; AutoMapper.AutoMapperMappingException: Trying to map System.String to System.String. Using mapping configuration for System.String to System.String Destination property: Comment Exception of type 'AutoMapper.AutoMapperMappingException' was thrown. ---&gt; System.ArgumentException: Type 'System.String' does not have a default constructor at System.Linq.Expressions.Expression.New(Type type) at AutoMapper.DelegateFactory.CreateCtor(Type type) at AutoMapper.Mappers.ObjectCreator.CreateObject(Type type) at AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.CreateObject(ResolutionContext context) at AutoMapper.Mappers.TypeMapObjectMapperRegistry.NewObjectPropertyMapMappingStrategy.GetMappedObject(ResolutionContext context, IMappingEngineRunner mapper) at AutoMapper.Mappers.TypeMapObjectMapperRegistry.PropertyMapMappingStrategy.Map(ResolutionContext context, IMappingEngineRunner mapper) at AutoMapper.Mappers.TypeMapMapper.Map(ResolutionContext context, IMappingEngineRunner mapper) at AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map(ResolutionContext context) --- End of inner exception stack trace --- at AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map(ResolutionContext context) at AutoMapper.Mappers.TypeMapObjectMapperRegistry.PropertyMapMappingStrategy.MapPropertyValue(ResolutionContext context, IMappingEngineRunner mapper, Object mappedObject, PropertyMap propertyMap) --- End </code></pre> <p>The Comment class that is mentioned:</p> <pre><code>public class InterviewComment { [Key] public int? InterviewCommentID { get; set; } [ForeignKey("Interview")] public int? InterviewID { get; set; } [CodeType(CodeTypeEnum.CommentSection)] public int? CommentSectionCodeID { get; set; } [CodeType(CodeTypeEnum.CommentSource)] public int? CommentSourceCodeID { get; set; } [Display(Name = "Comment")] [StringLength(int.MaxValue)] public string Comment { get; set; } [Include] [Association("Interview_1-*_InterviewComment", "InterviewID", "InterviewID", IsForeignKey = true)] public virtual Interview Interview { get; set; } [ReadOnly(true)] [ForeignKey("ModifiedByUser")] public virtual ApplicationUser ApplicationUser { get; set; } [ReadOnly(true)] public string UserName { get { return ApplicationUser != null ? ApplicationUser.GetDisplayName() : null; } } [ReadOnly(true)] public int CreatedByUser { get; set; } [ReadOnly(true)] public DateTime CreatedDateTime { get; set; } [ReadOnly(true)] public int ModifiedByUser { get; set; } [ReadOnly(true)] public DateTime ModifiedDateTime { get; set; } } </code></pre> <p>I'm still reviewing recent commits to identify the change that is causing this. Any insight into the exception would be greatly appreciated.</p>
 

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