Help me with NullReferenceException, please?

Question

Hello, Please help me with this code. I am trying to retrieve data from my table row and I dont have a success for two days.
This is a piece of code, witch I think couse a trouble:
private void ViewDataForm_Load(object sender, EventArgs e)
{
DataTable dt = new DataTable("NewTable");
DataSet ds = new DataSet();
ds.Tables.Add(dt);
DataColumn column;
column = new DataColumn();
column.DataType = System.Type.GetType("System.Int32");
column.ColumnName = "id";
column.ReadOnly = true;
column.Unique = true;
dt.Columns.Add(column);
dt.Columns.Add("Month", typeof(String));
dt.Columns.Add("Balance", typeof(String));
DataColumn[] PrimaryKeyColumns = new DataColumn[1];
PrimaryKeyColumns[0] = dt.Columns["id"];
dt.PrimaryKey = PrimaryKeyColumns;
String sqlQuery = "";
int counter = 0;
System.Data.SqlServerCe.SqlCeConnection conn = new System.Data.SqlServerCe.SqlCeConnection(
("Data Source=newDB.sdf;Max Database Size=2047"));
try
{
//Let's assing our sql data reader
SqlCeDataReader myReader = null;
// Let's connect to it
conn.Open();
System.Data.SqlServerCe.SqlCeCommand cmd = conn.CreateCommand();
sqlQuery = "SELECT SUM(income-expense) AS Balance, date_y AS Date FROM Income WHERE date = '" + comboBoxCurrentlyShowingYear.SelectedItem + "' GROUP BY date_y ORDER BY " + comboBoxSortBy.SelectedItem + " " + comboBoxASCDESC.SelectedItem;
cmd.CommandText = sqlQuery;
myReader = cmd.ExecuteReader();
while (myReader.Read())
{
counter++;
dt.Rows.Add(counter, myReader[1].ToString(), myReader[0].ToString());
}
dataGridIncome.DataSource = ds.DefaultViewManager.CreateDataView(dt);
int primaryKey = dataGridIncome.CurrentRowIndex + 1;
DataRow findRow = ds.Tables[0].NewRow();
findRow = dt.Rows.Find(primaryKey);
//!#!#! I get a message after that Message.Show() method. It says: NullReferenceException was unhandled. !#!#!
MessageBox.Show("Current row index: " + findRow[0].ToString() + "
Month: " + findRow[1].ToString() + "
Balance: " + findRow[2].ToString());
}
finally
{
//Close that connection NOW
conn.Close();
ds.Tables.Clear();
}
} I get an error after proceding Message.Show method.
If someone, please, can help me.

Sam Hobbs · Accepted Answer

Are you sure you get the error after the Message.Show? Do you mean MessageBox .Show?
Also, if the error occurs in the MessageBox.Show then that could happen if the row is not found. You should check findRow for null before using it.

Saulius · Answer

Thank you guys. Problwem solved. After i check if row exists everything goes fine.

Sam Hobbs · Answer

It could be many things but probably the data is not equal even though it looks equal to you. You need to look closely at the data. I don't know what the data type is but if it is string then perhaps there is a space someplace that you don't see.

Saulius · Answer

Hello, thankls for trying to help me. After checking if the row exists: It says row does not exist? Howe does it possible? Becouse DataGrid see those rows and if I am trying to retrieve them with Find() method, row is not found. What could it be?

Kirtan Patel · Answer

Friend ,
Modify your code like below
if my solution works then check " Do you like this answer " check box :)
private void ViewDataForm_Load( object sender, EventArgs e)
{
DataTable dt = new DataTable ( "NewTable" );
DataSet ds = new DataSet ();
ds.Tables.Add(dt);
DataColumn column;
column = new DataColumn ();
column.DataType = System. Type .GetType( "System.Int32" );
column.ColumnName = "id" ;
column.ReadOnly = true ;
column.Unique = true ;
dt.Columns.Add(column);
dt.Columns.Add( "Month" , typeof ( String ));
dt.Columns.Add( "Balance" , typeof ( String ));
DataColumn [] PrimaryKeyColumns = new DataColumn [1];
PrimaryKeyColumns[0] = dt.Columns[ "id" ];
dt.PrimaryKey = PrimaryKeyColumns;
String sqlQuery = "" ;
int counter = 0;
System.Data.SqlServerCe.SqlCeConnection conn = new System.Data.SqlServerCe.SqlCeConnection(
( "Data Source=newDB.sdf;Max Database Size=2047" ));
try
{
//Let's assing our sql data reader
SqlCeDataReader myReader = null ;
// Let's connect to it
conn.Open();
System.Data.SqlServerCe.SqlCeCommand cmd = conn.CreateCommand();
sqlQuery = "SELECT SUM(income-expense) AS Balance, date_y AS Date FROM Income WHERE date = '" + comboBoxCurrentlyShowingYear.SelectedItem + "' GROUP BY date_y ORDER BY " + comboBoxSortBy.SelectedItem + " " + comboBoxASCDESC.SelectedItem;
cmd.CommandText = sqlQuery;
myReader = cmd.ExecuteReader();
while (myReader.Read())
{
counter++;
dt.Rows.Add(counter, myReader[1].ToString(), myReader[0].ToString());
}
dataGridIncome.DataSource = ds.DefaultViewManager.CreateDataView(dt);
int primaryKey = dataGridIncome.CurrentRowIndex + 1;
DataRow findRow = ds.Tables[0].NewRow();
if (dt.Rows.Find(primaryKey) != null )
{
findRow = dt.Rows.Find(primaryKey);
}
else
{
MessageBox .Show( "Row Not Found !!" );
}
//!#!#! I get a message after that Message.Show() method. It says:  NullReferenceException was unhandled. !#!#!
MessageBox .Show( "Current row index: " + findRow[0].ToString() + "
Month: " + findRow[1].ToString() + "
Balance: " + findRow[2].ToString());
}
finally
{
//Close that connection NOW
conn.Close();
ds.Tables.Clear();
}
}