How to insert NULL for INTEGER data type in SQL Server from C# .Net

This code will insert Null value in Int data type column

C#

protected void Save(object sender, EventArgs e)
{
    int no = 0;
    string constr = ConfigurationManager.ConnectionStrings["Constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        string query = "insert into tblCheckIn values (@Number)";
        using (SqlCommand cmd = new SqlCommand(query))
        {
            cmd.Connection = con;
            if (no == 0)
            {
                cmd.Parameters.AddWithValue("@Number", DBNull.Value);
            }
            else
            {
                cmd.Parameters.AddWithValue("@Number", no);
            }
            con.Open();
            cmd.ExecuteNonQuery();
            con.Close();
        }
    }
}

SQL

You need to check some condition in InsertRecord method like below.

public static void InsertRecord(ProjectProfile model)
{
    // ..... my starting coding ...
    if (model.builder_id == 0)
    {
        cmd.Parameters.AddWithValue("@build_id", DBNull.Value);
    }
    else
    {
        cmd.Parameters.AddWithValue("@build_id", model.builder_id);
    }

    // ..... my end coding ...

}

Please refer the logic and implement it in your project. You can also refer this Reply In the same question.