Insert Null into database with Entity Framework sql

Question

private void BtnAdd_Click(object sender, EventArgs e)
{
    Model.Item items = new Model.Item
    {
        Code = Convert.ToInt32(txtCode.Text),
        Name = txtName.Text,
        MQCode = Convert.ToInt32(string.IsNullOrEmpty(txtMinmumQuantityNo.Text) ? null :   txtMinmumQuantityNo.Text)
    };
    db.Items.Add(items);
    db.SaveChanges();
}

Error

SqlException: The INSERT statement conflicted with the FOREIGN KEY constraint "FK_Items_MQ". The conflict occurred in database "C:\USERS\20101\DESKTOP\SIGMA V1\SIGMA V1\BIN\DEBUG\SIGMA.MDF", table "dbo.MQ", column 'MQCode'. The statement has been terminated.

You're not inserting NULL. Convert.ToInt32 converts null to 0. 0 isn't matching a record in the parent table. — madreflection
– madreflection, Commented Oct 23, 2019 at 16:37
Check the constraints on your foreign keys, some are not allowed to be null, some have to be unique. We cannot even see the type of MQCode here. — Holger
– Holger, Commented Oct 23, 2019 at 16:41
What can I use instead of Convert.ToInt32 And gives the result = null ?? — Ahmed Abdo
– Ahmed Abdo, Commented Oct 23, 2019 at 16:44

CPerson · Accepted Answer · 2019-10-23 16:42:45Z

1

According to the documentation (linked below), Convert.ToInt32 returns 0 when the string parameter is null.

As such, the following line is setting MQCode to 0 which is an invalid Foreign Key value for MQCode.

MQCode = Convert.ToInt32(string.IsNullOrEmpty(txtMinmumQuantityNo.Text) ? null :   txtMinmumQuantityNo.Text)

Consider instead using the following:

MQCode = string.IsNullOrEmpty(txtMinmumQuantityNo.Text) ? (int?)null : Convert.ToInt32(txtMinmumQuantityNo.Text)

This will either return a null or an integer.

https://learn.microsoft.com/en-us/dotnet/api/system.convert.toint32?view=netframework-4.8#System_Convert_ToInt32_System_String_

answered Oct 23, 2019 at 16:42

CPerson

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Comments

Ljubomir Bacovic · Accepted Answer · 2019-10-23 16:38:59Z

0

It looks like that field is not nullable. It must have an actual value.

answered Oct 23, 2019 at 16:38

Ljubomir Bacovic

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