The INSERT statement conflicted with the FOREIGN KEY??

Question

Keep getting the error: The INSERT statement conflicted with the FOREIGN KEY constraint "FK_Threads_Users". table "dbo.Users", column 'uid'.

Users table:

CREATE TABLE [dbo].[Users] (

[uid] INT IDENTITY (1, 1) NOT NULL,

[username] VARCHAR (14) NOT NULL,

[firstName] VARCHAR (20) NULL,

[lastName] VARCHAR (20) NULL,

[gender] VARCHAR (6) NULL,

[picture] VARCHAR (MAX) NULL,

CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED ([uid] ASC)
);

Threads table:

CREATE TABLE [dbo].[Threads] (

[ThreadId] INT IDENTITY (1, 1) NOT NULL,

[TopicId] INT NULL,

[Title] VARCHAR (50) NULL,

[Content] NTEXT NULL,

[PostedBy] VARCHAR (30) NULL,

[PostedDate] DATETIME NULL,

[uid] INT NULL,

CONSTRAINT [PK_Threads] PRIMARY KEY CLUSTERED ([ThreadId] ASC),

CONSTRAINT [FK_Threads_Users] FOREIGN KEY ([uid]) REFERENCES [dbo].[Users] ([uid]),

CONSTRAINT [FK_Threads_Threads] FOREIGN KEY ([TopicId]) REFERENCES [dbo].[Topics] ([TopicId])

);

SqlConnection conn;

SqlCommand comm;

conn = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=" + Server.MapPath("~\\App_Data\\ForumDB.mdf") + ";Integrated Security=True;User Instance=True");

conn.Open();

comm = new SqlCommand("INSERT INTO Threads values(" + Convert.ToInt32(Session["tid"].ToString()) + ",'" + Subject.Text + "','" + Post.Text + "','" + Session["uname"].ToString() + "','" + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff") + "'," + Convert.ToInt32(Session["uid"]) + ")", conn);

int rows = comm.ExecuteNonQuery();

if (rows > 0)

{

Response.Redirect("threads.aspx?TopicId=" + Session["tid"].ToString());

}

conn.Close();

Vincent Maverick Durano · Answer

Everyone is noob when learning something new so don't feel bad because I was once a noob too :) That's why you need to understand how stuff works and learn from it one step at a time

Ravi Rai · Answer

do you have skype by any chance? i'm seriously stuck thanks

Ravi Rai · Answer

i am such a noob at asp.net and c sharp. this sucks !

Vincent Maverick Durano · Answer

Before referencing a Session value make sure that you check for null first Your Session may/will return string but you should do a null check on the Session object itself like so: if(Session[KeyName] != null){ //your code here to access the Session value }

Abhineet Srivastava · Answer

Nah..i don't have Skype here on My Laptop But You can Ask here so That Other one can also hep you to sort out the issue

Ravi Rai · Answer

do you have skype? could you help me?

Abhineet Srivastava · Answer

Excuse Me.... String could have Null Value but Int not (Except you mark them Nullable)

Ravi Rai · Answer

the session uid is returning a string so it is not null. how would i go about doing what you said?

Abhineet Srivastava · Answer

Check the session null ondition before converting into .toString().use Convert.tostring() Instead.

Ravi Rai · Answer

I sorted out the problem by sorting out my database values however now i am faced with another problem.... the SessionID is failing to convert to INT. in my SQL statement i have: comm.Parameters.AddWithValue(@f Convert.ToInt32(Session[uid].ToString())); In my debugger it says: Session[uid] gkxmclggolihegy5owjrvgcw object {string} in my page load i have: if (Page.User.Identity.IsAuthenticated == true) { Threadbutton.Visible = true; ImageButton1.Visible = true; Session[tid] = Request.QueryString[TopicId]; Session[uname] = Page.User.Identity.Name; Session[uid] = this.Session.SessionID; }

Vincent Maverick Durano · Answer

The error message says you are trying to insert data that has a foreign key value that doesn't exist in the parent table. For example you might have Users with Id values of 1234 and 5 but you are trying to add a Thread with an Users of 6 (or more likely 0). You should use a debugger to double check the foreign key value. Adding to that I will not recommend you to append the TextBox values directly into your SQL statements because that would leads you to SQL Injection  use Parameterized Query instead for security and more cleaner codes.

Abhineet Srivastava · Answer

You are inserting the some value of Uid in thread table which are not present in User Table... First Check That Is that Uid value exist in User table or not... If Not Then you need to Insert That Uid value to User table first.

Ravi Rai · Answer

Hi as you can see in my dbo.Users i have the PK as uid

Manoj Bhoir · Answer

Hi I don't think there is any thing wrong in your code. Please check that User Id i.e. uid you are inserting into the dbo.Threads table must exist in your dbo.Users table i.e. Primary Key Table. For more details about Primary Key and Foreign Key see this link https://msdn.microsoft.com/en-us/library/ms179610.aspx