如何在测验制作web应用程序中修复此错误

我在ASP中开发了一个类似的测验引擎。. NET网站，但我只是添加了一个新的表来设计数据库。数据库的原始设计由以下三个表组成:

测验表:测验id，标题，描述

问题表: QuestionID, Question, Answer1, Answer2, Answer3, Answer4, CorrectAnswer, answerexplain, QuestionOrder, QuizID

UserQuiz Table: UserQuizID, QuizID, DateTimeComplete, Score, Username

每个表中的第一个属性是该表的主键

我所做的只是添加一个新表，它是:

User Table: Username, Name, Job, Address (Username为主键)

对于代码隐藏，我没有触及任何东西，但是当我试图执行代码时，它给了我一个错误。后面的代码是:

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class Results : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        ArrayList al = (ArrayList)Session["AnswerList"];
        if (al == null)
        {
            Response.Redirect("default.aspx");
        }
        resultGrid.DataSource = al;
        resultGrid.DataBind();
        // Save the results into the database.
        if (IsPostBack == false)
        {
            // Calculate score
            double questions = al.Count;
            double correct = 0.0;

            for (int i = 0; i < al.Count; i++)
            {
                Answer a = (Answer)al[i];
                if (a.Result == Answer.ResultValue.Correct)
                    correct++;
            }
            double score = (correct / questions) * 100;
            SqlDataSource userQuizDataSource = new SqlDataSource();
            userQuizDataSource.ConnectionString = ConfigurationManager.ConnectionStrings["testConnectionString"].ToString();
            userQuizDataSource.InsertCommand = "INSERT INTO [UserQuiz] ([QuizID], [DateTimeComplete], [Score], [UserName]) VALUES (@QuizID, @DateTimeComplete, @Score, @UserName)";
            userQuizDataSource.InsertParameters.Add("QuizID", Session["QuizID"].ToString());
            userQuizDataSource.InsertParameters.Add("DateTimeComplete", DateTime.Now.ToString());
            userQuizDataSource.InsertParameters.Add("Score", score.ToString());
            userQuizDataSource.InsertParameters.Add("UserName", User.Identity.Name);
            int rowsAffected = userQuizDataSource.Insert();
            if (rowsAffected == 0)
            {
                // Let's just notify that the insertion didn't
                // work, but let' s continue on ...
                errorLabel.Text = "There was a problem saving your quiz results into our database.  Therefore, the results from this quiz will not be displayed on the list on the main menu.";

            }
        }

    }
    protected void resultGrid_SelectedIndexChanged(object sender, EventArgs e)
    {
        SqlDataSource1.FilterExpression = "QuestionOrder=" + resultGrid.SelectedValue;
    }
}

错误:

INSERT语句与外键约束"FK_UserQuiz_employee"冲突。冲突发生在数据库"psspdb"，表"dbo"。employee"，列"Username"。语句已被终止。

源错误:

<>之前第50行:userQuizDataSource.InsertParameters。添加("用户名",User.Identity.Name);51行:第52行:int rowsAffected = userQuizDataSource.Insert()第53行:if (rowsAffected == 0)54行:之前

UserQuiz表中的Username是User表中Username的外键。我知道，但是我应该做什么来解决这个问题

public bool UserExists(string UserName)
{
    DataTable table = new DataTable("table");
    string connectionString = ConfigurationManager.ConnectionStrings["testConnectionString"].ToString();
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        SqlCommand command = new SqlCommand();
        command.Connection = connection;
        command.CommandType = System.Data.CommandType.StoredProcedure;
        command.CommandText = "SELECT COUNT(UserName) FROM User WHERE UserName = " + UserName;
        try
        {
            connection.Open();
            object userName = command.ExecuteScalar();
            return userName != null;
        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);
        }
    }
}

if(UserExists(User.Identity.Name))
{
    // Your insert logic goes here...
}