How do I get values from a SQL database into textboxes using C

Question

I m creating a booking management system and I am having problems trying to get data from a SQL database and insert into a group of textboxes of my application    I want to show the customer details  when a button is clicked  in a DataGridView  but when I click the button  the application throws an exception with the following error message       Invalid attempt to read when no data is present    I have attached a screenshot of the screen where I want to view customer details  and the code for the button  which will eventually show customer details in the respective textboxes  Any help would be greatly appreciated       SqlConnection sc   new SqlConnection  Data Source localhost Initial Catalog LoginScreen Integrated Security True            SqlCommand com   new SqlCommand            com Connection   sc          sc Open            SqlDataReader read    null           com CommandText     select   from Pending Tasks            read   com ExecuteReader            CustID Text    read  Customer ID   ToString             CustName Text    read  Customer Name   ToString             Add1 Text    read  Address 1   ToString             Add2 Text    read  Address 2   ToString             PostBox Text    read  Postcode   ToString             PassBox Text    read  Password   ToString             DatBox Text    read  Data Important   ToString             LanNumb Text    read  Landline   ToString             MobNumber Text    read  Mobile   ToString             FaultRep Text    read  Fault Report   ToString             sc Close

User · Answer

using  SqlConnection connection    new SqlConnection  Data Source localhost Initial Catalog LoginScreen Integrated Security True          SqlCommand command       new SqlCommand  select   from Pending Tasks WHERE CustomerId       connection       connection Open         SqlDataReader read  command ExecuteReader         while  read Read                  CustID Text    read  Customer ID   ToString             CustName Text    read  Customer Name   ToString             Add1 Text    read  Address 1   ToString             Add2 Text    read  Address 2   ToString             PostBox Text    read  Postcode   ToString             PassBox Text    read  Password   ToString             DatBox Text    read  Data Important   ToString             LanNumb Text    read  Landline   ToString             MobNumber Text    read  Mobile   ToString             FaultRep Text    read  Fault Report   ToString               read Close        Make sure you have data in the query   select   from Pending Tasks and you are using  using System Data SqlClient

User · Answer

read   com ExecuteReader    SqlDataReader has a function Read   that reads the next row from your query s results and returns a bool whether it found a next row to read or not  So you need to check that before you actually get the columns from your reader  which always just gets the current row that Read   got   Or preferably make a loop while read Read    if your query returns multiple rows

User · Answer

If you want to display single value access from database into textbox  please refer to the code below   SqlConnection con new SqlConnection  connection string    SqlCommand cmd new SqlConnection SqlQuery Con   Con Open    TextBox1 Text cmd ExecuteScalar    Con Close      or  SqlConnection con new SqlConnection  connection string    SqlCommand cmd new SqlConnection SqlQuery Con   Con Open    SqlDataReader dr new SqlDataReadr    dr cmd Executereader    if dr read          TextBox1 Text dr GetValue 0  Tostring      Con Close

User · Answer

Make a connection and open it   con   new OracleConnection  Data Source  DESCRIPTION  ADDRESS LIST  ADDRESS  PROTOCOL TCP  HOST localhost  PORT 1521    CONNECT DATA  SERVER DEDICATED  SERVICE NAME  lt database name gt     User Id   lt userid gt   Password   lt password gt     con Open      Write the select query    string sql    select   from Pending Tasks     Create a command object   OracleCommand cmd   new OracleCommand sql  con     Execute the command and put the result in a object to read it   OracleDataReader r   cmd ExecuteReader      now start reading from it   while  read Read       CustID Text    read  Customer ID   ToString      CustName Text    read  Customer Name   ToString      Add1 Text    read  Address 1   ToString      Add2 Text    read  Address 2   ToString      PostBox Text    read  Postcode   ToString      PassBox Text    read  Password   ToString      DatBox Text    read  Data Important   ToString      LanNumb Text    read  Landline   ToString      MobNumber Text    read  Mobile   ToString      FaultRep Text    read  Fault Report   ToString       read Close      Add this too using Oracle ManagedDataAccess Client

User · Answer

The line reader Read   is missing in your code  You should add it  It is the function which actually reads data from the database   string conString    Data Source localhost Initial Catalog LoginScreen Integrated Security True   SqlConnection con   new SqlConnection conString    string selectSql    select   from Pending Tasks   SqlCommand com   new SqlCommand selectSql  con    try       con Open         using  SqlDataReader read   cmd ExecuteReader                  while reader Read                          CustID Text    read  Customer ID   ToString                 CustName Text    read  Customer Name   ToString                 Add1 Text    read  Address 1   ToString                 Add2 Text    read  Address 2   ToString                 PostBox Text    read  Postcode   ToString                 PassBox Text    read  Password   ToString                 DatBox Text    read  Data Important   ToString                 LanNumb Text    read  Landline   ToString                 MobNumber Text    read  Mobile   ToString                 FaultRep Text    read  Fault Report   ToString                       finally       con Close        EDIT   This code works supposing you want to write the last record to your textboxes  If you want to apply a different scenario  like for example to read all the records from database and to change data in the texboxes when you click the Next button  you should create and use your own Model  or you can store data in the DataTable and refer to them later if you wish

[c#] How do I get values from a SQL database into textboxes using C#?

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