存储过程不更新记录

我有一个c#函数，它用输入参数调用SQL Server存储过程。当直接通过SQL Server Management Studio执行存储过程时，该存储过程运行良好，因此我认为问题一定在c#方面，但我一辈子都无法解决。我已经为其他人搜索了以前出现此问题的所有时间，但一直找不到解决方案。如果最终无法确定出了什么问题，我们将非常感谢一些调试技巧，因为我不太擅长更高级的故障排除。

这是c#函数：

protected void UpdateProfile(object sender, EventArgs e)
    {
        string connstring = ConfigurationManager.ConnectionStrings["TimeHubDBCS"].ConnectionString;
        using (SqlConnection conn = new SqlConnection(connstring))
        {
            try
            {
                SqlCommand cmd = new SqlCommand("spUpdateProfile", conn);
                cmd.CommandType = System.Data.CommandType.StoredProcedure;
                cmd.Parameters.Add("@UserId", SqlDbType.VarChar).Value = userloggedin.Text;
                cmd.Parameters.Add("@FirstName", SqlDbType.VarChar).Value = first_name.Text;
                cmd.Parameters.Add("@LastName", SqlDbType.VarChar).Value = last_name.Text;
                cmd.Parameters.Add("@MiddleInitial", SqlDbType.VarChar).Value = middle_initial.Text;
                cmd.Parameters.Add("@Assignment", SqlDbType.VarChar).Value = ddl_assignment.Text;
                cmd.Parameters.Add("@Rank", SqlDbType.VarChar).Value = rank.Text;
                cmd.Parameters.Add("@Star", SqlDbType.VarChar).Value = star.Text;
                cmd.Parameters.Add("@ContactPhone", SqlDbType.VarChar).Value = contact_phone.Text;
                cmd.Parameters.Add("@PhoneType", SqlDbType.VarChar).Value = phone_type.Text;
                cmd.Parameters.Add("@Email", SqlDbType.VarChar).Value = email.Text;
                cmd.Parameters.Add("@Shift", SqlDbType.VarChar).Value = ddl_shift.Text;
                cmd.Parameters.Add("@ModifyDate", SqlDbType.VarChar).Value = DateTime.Now.ToString();
                cmd.Parameters.Add("@ModifiedBy", SqlDbType.VarChar).Value = userloggedin.Text;
                cmd.Parameters.Add("@StatusId", SqlDbType.VarChar).Value = "active";
                conn.Open();
                cmd.ExecuteNonQuery();
                Response.Write("Profile updated successfully!");
            }
            catch (Exception ex)
            {
                Response.Write("Profile update error:  " + ex.Message);
            }
        }
    }

以下是sql server存储过程：

ALTER PROCEDURE spUpdateProfile
@UserId         VARCHAR(200)    =   NULL    ,
@FirstName      VARCHAR(200)    =   NULL    ,
@LastName       VARCHAR(200)    =   NULL    ,
@MiddleInitial  VARCHAR(200)    =   NULL    ,
@Assignment     VARCHAR(200)    =   NULL    ,
@Rank           VARCHAR(200)    =   NULL    ,
@Star           VARCHAR(200)    =   NULL    ,
@ContactPhone   VARCHAR(200)    =   NULL    ,
@PhoneType      VARCHAR(200)    =   NULL    ,
@Email          VARCHAR(200)    =   NULL    ,
@Shift          VARCHAR(200)    =   NULL    ,
@ModifyDate     VARCHAR(200)    =   NULL    ,
@ModifiedBy     VARCHAR(200)    =   NULL    ,
@StatusId       VARCHAR(200)    =   NULL    
AS
BEGIN
UPDATE dbo.users
    SET
        first_name          =   @FirstName          ,
        last_name           =   @LastName           ,
        middle_initial      =   @MiddleInitial      ,
        assignment          =   @Assignment         ,
        user_rank           =   @Rank               ,
        user_star           =   @Star               ,
        contact_phone       =   @ContactPhone       ,
        phone_type          =   @PhoneType          ,
        email               =   @Email              ,
        regular_shift       =   @Shift              ,
        modify_date         =   @ModifyDate         ,
        modified_by         =   @ModifiedBy         ,
        status_id           =   @StatusId           
    WHERE
        user_id             =   @UserId
END