Convert string to HierarchyId in Fluent API (EF Core) using "HasConversion()" or any other method?

I am using FileTables with EF Core Code First approach. I have used stored procedure to get the Path_Locator (PK) from FileTable (named as 'DocumentStore') in string and now attempting to insert the same in another table where I store information about that file. I have manually added the Foreign Key constraint in a table which references FileTable using code first migrations. I therefore want to add retrieved Path_Locator (as string) to insert into another table. But the problem here is that I retrieved the value in string but the foreign key constraint has a type of hierarchyid.

This is how I added in my DbContext class

builder.Entity<ArticleFiles>(entity => {
     entity.Property(x => x.PathLocator).HasColumnType("hierarchyid");
});

Following is the stack trace:

    Microsoft.EntityFrameworkCore.Database.Command[20102]
      Failed executing DbCommand (87ms) [Parameters=[@p0='?' (DbType = Int32), @p1='?' (Size = 450), @p2='?' (Size = 4000), @p3='?' (Size = 4000), @p4='?' (DbType = Int32), @p5='?' (Size = 450), @p6='?' (DbType
 = Boolean)], CommandType='Text', CommandTimeout='30']
      SET NOCOUNT ON;
      INSERT INTO [ArticleFiles] ([ArticleId], [PathLocator], [FileDescription], [FileName], [FileTypeId], [GeneratedFileName], [IsAttachment])
      VALUES (@p0, @p1, @p2, @p3, @p4, @p5, @p6);
fail: Microsoft.EntityFrameworkCore.Update[10000]
      An exception occurred in the database while saving changes for context type 'PublicationFinal.Data.DataContext'.
      Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details.
       ---> Microsoft.Data.SqlClient.SqlException (0x80131904): A .NET Framework error occurred during execution of user-defined routine or aggregate "hierarchyid":
      Microsoft.SqlServer.Types.HierarchyIdException: 24001: SqlHierarchyId.Parse failed because the input string '0xFD92800AD195392FF75255D5F1E836FB6FD89006BFD8987C037B7061F86242EF9612661F45F8F1084C' is not a
valid string representation of a SqlHierarchyId node.
      Microsoft.SqlServer.Types.HierarchyIdException:
         at Microsoft.SqlServer.Types.SqlHierarchyId.Parse(SqlString input)
      .
      The statement has been terminated.
         at Microsoft.Data.SqlClient.SqlCommand.<>c.<ExecuteDbDataReaderAsync>b__164_0(Task`1 result)
         at System.Threading.Tasks.ContinuationResultTaskFromResultTask`2.InnerInvoke()
         at System.Threading.Tasks.Task.<>c.<.cctor>b__274_0(Object obj)
         at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
      --- End of stack trace from previous location where exception was thrown ---
         at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
         at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
      --- End of stack trace from previous location where exception was thrown ---
         at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
         at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
         at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
         at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)
      ClientConnectionId:f2ef6681-7b4c-41bb-b313-b8c6acbfd34a
      Error Number:6522,State:2,Class:16
         --- End of inner exception stack trace ---
         at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)
         at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable`1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
         at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable`1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
         at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList`1 entriesToSave, CancellationToken cancellationToken)
         at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(DbContext _, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
         at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellatio
nToken)
         at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details.
 ---> Microsoft.Data.SqlClient.SqlException (0x80131904): A .NET Framework error occurred during execution of user-defined routine or aggregate "hierarchyid":
Microsoft.SqlServer.Types.HierarchyIdException: 24001: SqlHierarchyId.Parse failed because the input string '0xFD92800AD195392FF75255D5F1E836FB6FD89006BFD8987C037B7061F86242EF9612661F45F8F1084C' is not a valid
string representation of a SqlHierarchyId node.
Microsoft.SqlServer.Types.HierarchyIdException:
   at Microsoft.SqlServer.Types.SqlHierarchyId.Parse(SqlString input)
.
The statement has been terminated.
   at Microsoft.Data.SqlClient.SqlCommand.<>c.<ExecuteDbDataReaderAsync>b__164_0(Task`1 result)
   at System.Threading.Tasks.ContinuationResultTaskFromResultTask`2.InnerInvoke()
   at System.Threading.Tasks.Task.<>c.<.cctor>b__274_0(Object obj)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location where exception was thrown ---
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)
ClientConnectionId:f2ef6681-7b4c-41bb-b313-b8c6acbfd34a
Error Number:6522,State:2,Class:16
   --- End of inner exception stack trace ---
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable`1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable`1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList`1 entriesToSave, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(DbContext _, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellationToken
)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)

Can I use some method in the fluentapi to convert this string to HierarchyId before I put it into database?

I guess you need tostring function but try to answer totally.

You can convert hierarchyid to string in a new column or temp table, then use this.

For example, if you have this table:

 CREATE TABLE SimpleDemo  
(
    Level hierarchyid NOT NULL,  
    Location nvarchar(30) NOT NULL,  
    LocationType nvarchar(9) NULL
);
Go
INSERT SimpleDemo  
    VALUES   
('/1/', 'Europe', 'Continent'),  
('/2/', 'South America', 'Continent'),  
('/1/1/', 'France', 'Country'),  
('/1/1/1/', 'Paris', 'City'),  
('/1/2/1/', 'Madrid', 'City'),  
('/1/2/', 'Spain', 'Country'),  
('/3/', 'Antarctica', 'Continent'),  
('/2/1/', 'Brazil', 'Country'),  
('/2/1/1/', 'Brasilia', 'City'),  
('/2/1/2/', 'Bahia', 'State'),  
('/2/1/2/1/', 'Salvador', 'City'),  
('/3/1/', 'McMurdo Station', 'City');
Go

You can find results like:

SELECT CAST(Level AS nvarchar(100)) AS [Converted Level], *   
    FROM SimpleDemo ORDER BY Level

and you can use function :

Select Level.ToString()
From SimpleDemo

I hope this helpfull

If you want to use c# function for convert this hierarchyid you can use this code, but you should install SSDT, SQLCLIENT :

using System;  
using System.Collections;  
using System.Text;  
using Microsoft.SqlServer.Server;  // SqlFunction Attribute
using Microsoft.SqlServer.Types;   // SqlHierarchyId

public partial class HierarchyId_Operations  
{  
    [SqlFunction(FillRowMethodName = "FillRow_ListAncestors")]
    public static IEnumerable ListAncestors(SqlHierarchyId h)
    {  
        while (!h.IsNull)  
        {  
            yield return (h);  
            h = h.GetAncestor(1);  
        }  
    }  
    public static void FillRow_ListAncestors(
        Object obj,
        out SqlHierarchyId ancestor
        )
    {  
        ancestor = (SqlHierarchyId)obj;  
    }  

    public static HierarchyId CommonAncestor(
        SqlHierarchyId h1,
        HierarchyId h2
        )  
    {  
        while (!h1.IsDescendantOf(h2))  
            h1 = h1.GetAncestor(1);  

        return h1;  
    }  
}

You can find this sample in here