Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.

This is my UserRoleList.aspx.cs Code where i am passing the session variable to the page Default.aspx.cs

And the error is:

Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.

I have gone through many pages , and tried by making the AllowDbNull property making True and then different things.

Please help me out, where am i making the mistake and aslo suggest, if their any alternative

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;

public partial class Forms_RolesMgt_RoleList_UserRoleList : System.Web.UI.Page
{
    
    protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["userName"] == null)
            Response.Redirect("~/Login.aspx");

        if (!Page.IsPostBack)
        {
            if (!Page.User.IsInRole("Others_Roles_Add"))
                Response.Redirect("~/unauthorized.aspx");

            getUserRoles();
        }
    }
   
    private void getUserRoles()
    {
        DSRolesTableAdapters.aspnet_RoleUsersTableAdapter userRoleAdapter = new DSRolesTableAdapters.aspnet_RoleUsersTableAdapter();
        
        DataTable dt= new DataTable();
       dt = userRoleAdapter.GetDataUser();
       UserGridView.DataSource = dt;
       UserGridView.DataBind();
        
    }
      
    protected void UserNameIdGrdView_SelectedIndexChanged(object sender, EventArgs e)
    {

    }
    protected void Send(object sender, EventArgs e)
    {
        GridViewRow gr = ((sender as LinkButton).NamingContainer as GridViewRow);
        Session["UserId"] = gr.Cells[0].Text.Trim();
        Session["UserName"] = gr.Cells[1].Text.Trim();
        Response.Redirect("~/Forms/RolesMgt/RoleList/Default.aspx");
    }
}

 This is the code of the second page Default.aspx.cs where i have to user the session varaible to pass in the SQL fucntion named GetDataByUserId as shown below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlTypes;

public partial class Forms_RolesMgt_RoleList_Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            DSRolesTableAdapters.aspnet_RoleUsersTableAdapter userRoleAdapter = new DSRolesTableAdapters.aspnet_RoleUsersTableAdapter();
            DataTable dt = new DataTable();
            Guid user = Guid.NewGuid();
            user = Guid.Parse(Session["UserId"] as string);
            Response.Write(user);
            dt = userRoleAdapter.GetDataByUserId(user);//er//ror coming at this line
            UserRolesGrdView.DataSource = dt;
            UserRolesGrdView.DataBind();

        }
    }
}