Pass Dictionary to Stored Procedure T-SQL

The accepted answer of using a TVP is generally correct, but needs some clarification based on the amount of data being passed in. Using a DataTable is fine (not to mention quick and easy) for smaller sets of data, but for larger sets it does not scale given that it duplicates the dataset by placing it in the DataTable simply for the means of passing it to SQL Server. So, for larger sets of data there is an option to stream the contents of any custom collection. The only real requirement is that you need to define the structure in terms of SqlDb types and iterate through the collection, both of which are fairly trivial steps.

A simplistic overview of the minimal structure is shown below, which is an adaptation of the answer I posted on How can I insert 10 million records in the shortest time possible?, which deals with importing data from a file and is hence slightly different as the data is not currently in memory. As you can see from the code below, this setup is not overly complicated yet highly flexible as well as efficient and scalable.

SQL object # 1: Define the structure

-- First: You need a User-Defined Table Type
   SortOrderNumber INT NOT NULL

SQL object # 2: Use the structure

-- Second: Use the UDTT as an input param to an import proc.
--         Hence "Tabled-Valued Parameter" (TVP)
   @ImportTable    dbo.IDsAndOrderNumbers READONLY

-- maybe clear out the table first?
TRUNCATE TABLE SchemaName.TableName;

INSERT INTO SchemaName.TableName (ID, SortOrderNumber)
    SELECT  tmp.ID,
    FROM    @ImportTable tmp;

-- OR --

some other T-SQL

-- optional return data
SELECT @NumUpdates AS [RowsUpdated],
       @NumInserts AS [RowsInserted];

C# code, Part 1: Define the iterator/sender

using System.Collections;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using Microsoft.SqlServer.Server;

private static IEnumerable<SqlDataRecord> SendRows(Dictionary<string,int> RowData)
   SqlMetaData[] _TvpSchema = new SqlMetaData[] {
      new SqlMetaData("ID", SqlDbType.NVarChar, 4000),
      new SqlMetaData("SortOrderNumber", SqlDbType.Int)
   SqlDataRecord _DataRecord = new SqlDataRecord(_TvpSchema);
   StreamReader _FileReader = null;

      // read a row, send a row
      foreach (KeyValuePair<string,int> _CurrentRow in RowData)
         // You shouldn't need to call "_DataRecord = new SqlDataRecord" as
         // SQL Server already received the row when "yield return" was called.
         // Unlike BCP and BULK INSERT, you have the option here to create an
         // object, do manipulation(s) / validation(s) on the object, then pass
         // the object to the DB or discard via "continue" if invalid.
         _DataRecord.SetString(0, _CurrentRow.ID);
         _DataRecord.SetInt32(1, _CurrentRow.sortOrderNumber);

         yield return _DataRecord;

C# code, Part 2: Use the iterator/sender

public static void LoadData(Dictionary<string,int> MyCollection)
   SqlConnection _Connection = new SqlConnection("{connection string}");
   SqlCommand _Command = new SqlCommand("ImportData", _Connection);
   SqlDataReader _Reader = null; // only needed if getting data back from proc call

   SqlParameter _TVParam = new SqlParameter();
   _TVParam.ParameterName = "@ImportTable";
// _TVParam.TypeName = "IDsAndOrderNumbers"; //optional for CommandType.StoredProcedure
   _TVParam.SqlDbType = SqlDbType.Structured;
   _TVParam.Value = SendRows(MyCollection); // method return value is streamed data
   _Command.CommandType = CommandType.StoredProcedure;


      // Either send the data and move on with life:
      // OR, to get data back from a SELECT or OUTPUT clause:
      SqlDataReader _Reader = _Command.ExecuteReader();
       Do something with _Reader: If using INSERT or MERGE in the Stored Proc, use an
       OUTPUT clause to return INSERTED.[RowNum], INSERTED.[ID] (where [RowNum] is an
       IDENTITY), then fill a new Dictionary<string, int>(ID, RowNumber) from
       _Reader.GetString(0) and _Reader.GetInt32(1). Return that instead of void.
      _Reader.Dispose(); // optional; needed if getting data back from proc call

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