System error при insert

        Dim cmdInsVS As SqlCommand = New SqlCommand()
        cmdInsVS.CommandText = "Insert into VacancySkill (VacancyId,SkillId) values (@pVacancyId,@pSkillId)"
        cmdInsVS.Connection = cnObj.cn

For i = 0 To CType(lbSkills.DataSource, DataTable).Rows.Count - 1
         cmdInsVS.Parameters.Add(New SqlParameter("@pVacancyId", SqlDbType.Int, 4)).Value = id.ToString
         cmdInsVS.Parameters.Add(New SqlParameter("@pSkillId", SqlDbType.Int, 4)).Value = CType(CType(lbSkills.DataSource, DataTable).Rows(i).Item("SkillId"), String)
         daSkillsVacancy.InsertCommand = cmdInsVS
         daSkillsVacancy.InsertCommand.ExecuteNonQuery()
next

CREATE TABLE VacancySkill] (
	VacancyId int NOT NULL ,
	SkillId int NOT NULL ,
	CONSTRAINT PK_VacancySkill PRIMARY KEY  CLUSTERED 
	(
		[VacancyId],
		[SkillId]
	)  ON PRIMARY )

            cmdInsVS.Parameters.Add(New SqlParameter("@pVacancyId", SqlDbType.Int, 4)).Value = id.ToString
            cmdInsVS.Parameters.Add(New SqlParameter("@pSkillId", SqlDbType.Int, 4)).Value = CType(CType(lbSkills.DataSource, DataTable).Rows(i).Item("SkillId"), String)
            daSkillsVacancy.InsertCommand = cmdInsVS
            daSkillsVacancy.InsertCommand.ExecuteNonQuery()

Dim cmdInsVS As SqlCommand = New SqlCommand()
cmdInsVS.CommandText = "Insert into VacancySkill (VacancyId,SkillId) values (@pVacancyId,@pSkillId)"
cmdInsVS.Connection = cnObj.cn
cmdInsVS.Parameters.Add(New SqlParameter("@pVacancyId", SqlDbType.Int, 4))
cmdInsVS.Parameters.Add(New SqlParameter("@pSkillId", SqlDbType.Int, 4))

daSkillsVacancy.InsertCommand = cmdInsVS


For i = 0 To CType(lbSkills.DataSource, DataTable).Rows.Count - 1
 cmdInsVS.Parameters.("@pVacancyId").Value =id.ToString
 cmdInsVS.Parameters.("@pSkillId").Value = CType(CType(lbSkills.DataSource, DataTable).Rows(i).Item("SkillId"), String)
daSkillsVacancy.InsertCommand.ExecuteNonQuery()
next