DotNet and Dapper. Incorrect syntax near ','.

c++
[HttpPost]
        public async Task<ActionResult<List<Step>>> PostNewStepInfo(string databaseName, List<Step> steps)
        {
            try
            {
                using var connection = new SqlConnection(_config.GetConnectionString("Default"));

                foreach (var step in steps)
                {
                    var test = await connection.ExecuteAsync($@"
                    INSERT INTO[{databaseName}].[dbo].[StepTable] ([Type], [ParentKey], [SubWorkflowCode], [Sequence], [WorkflowKey]) 
                    OUTPUT INSERTED.[Key] 
                    VALUES('{step.Type}', {step.ParentKey}, {step.SubWorkflowCode}, {step.Sequence}, {step.WorkflowKey});"
                        );

                    foreach (var parameter in step.Parameters)
                    {
                        await connection.ExecuteAsync($@"
                        INSERT INTO [{databaseName}].[dbo].[ParameterTable] ([Name], [Source], [Value], [WorkflowStepKey], [GroupCode], [EditedByCustomer]) 
                        VALUES ('{parameter.Name}', '{parameter.Source}', '{parameter.Value}', {test}, 'NULL', 0);"
                            );
                    }
                }
                return Ok(steps);
            }
            catch (SqlException ex) {
                Console.WriteLine($"SQL Exception: {ex.Message}");
                throw;
            }
        }

c++
[HttpPost]
        public async Task<ActionResult<List<Step>>> PostNewStepInfo(string databaseName, List<Step> steps)
        {
            try
            {
                using var connection = new SqlConnection(_config.GetConnectionString("Default"));

                foreach (var step in steps)
                {
                    var test = await connection.ExecuteAsync($@"
                    INSERT INTO[{databaseName}].[dbo].[StepTable] ([Type], [ParentKey], [SubWorkflowCode], [Sequence], [WorkflowKey]) 
                    OUTPUT INSERTED.[Key] 
                    VALUES('{step.Type}', {step.ParentKey}, {step.SubWorkflowCode}, {step.Sequence}, {step.WorkflowKey});"
                        );

                    foreach (var parameter in step.Parameters)
                    {
                        await connection.ExecuteAsync($@"
                        INSERT INTO [{databaseName}].[dbo].[ParameterTable] ([Name], [Source], [Value], [WorkflowStepKey], [GroupCode], [EditedByCustomer]) 
                        VALUES ('{parameter.Name}', '{parameter.Source}', '{parameter.Value}', {test}, 'NULL', 0);"
                            );
                    }
                }
                return Ok(steps);
            }
            catch (SqlException ex) {
                Console.WriteLine($"SQL Exception: {ex.Message}");
                throw;
            }
        }

[
  {
      "type": "a test",
      "parentKey": null,
      "subWorkflowCode": null,
      "sequence": 4,
      "workflowKey": 1,
      "parameters": [
          {
              "name": "od1",
              "source": "od1",
              "value": "od1"
          },
          {
              "name": "od2",
              "source": "od2",
              "value": "od2"
          }
      ]
  }
]

[
  {
      "type": "a test",
      "parentKey": null,
      "subWorkflowCode": null,
      "sequence": 4,
      "workflowKey": 1,
      "parameters": [
          {
              "name": "od1",
              "source": "od1",
              "value": "od1"
          },
          {
              "name": "od2",
              "source": "od2",
              "value": "od2"
          }
      ]
  }
]

(0x80131904): Incorrect syntax near ','.

(0x80131904): Incorrect syntax near ','.