I have a function like this
public void GetTablesWithUpperCaseName()
{
SqlConnectionStringBuilder objConnectionString = new SqlConnectionStringBuilder();
objConnectionString.DataSource = txtHost.Text;
objConnectionString.UserID = txtUsername.Text;
objConnectionString.Password = txtPassword.Text;
objConnectionString.InitialCatalog = Convert.ToString(cmbDatabases.SelectedValue);
SqlConnection sConnection = new SqlConnection(objConnectionString.ConnectionString);
//To Open the connection.
sConnection.Open();
//Query to select table_names that have their names in uppercase letters.
string selectTablesWithUppercaseName = @"SELECT
NAME
FROM
sysobjects
WHERE
UPPER(name) COLLATE Latin1_General_BIN = name COLLATE Latin1_General_BIN
AND
OBJECTPROPERTY(ID,N'IsTable')=1
AND
OBJECTPROPERTY(ID,N'IsMSShipped')=0 ";
//Create the command object
SqlCommand sCommand = new SqlCommand(selectTablesWithUppercaseName, sConnection);
try
{
//Create the dataset
DataSet dsListOfTablesWithUppercaseName = new DataSet("sysobjects");
//Create the dataadapter object
SqlDataAdapter sDataAdapter = new SqlDataAdapter(selectTablesWithUppercaseName, sConnection);
//Provides the master mapping between the sourcr table and system.data.datatable
sDataAdapter.TableMappings.Add("Table", "sysobjects");
//Fill the dataset
sDataAdapter.Fill(dsListOfTablesWithUppercaseName);
//Bind the result combobox with foreign key table names
DataViewManager dvmListOfForeignKeys = dsListOfTablesWithUppercaseName.DefaultViewManager;
dgResultView.DataSource = dsListOfTablesWithUppercaseName.Tables["sysobjects"];
}
catch(Exception ex)
{
//All the exceptions are handled and written in the EventLog.
EventLog log = new EventLog("Application");
log.Source = "MFDBAnalyser";
log.WriteEntry(ex.Message);
}
finally
{
//If connection is not closed then close the connection
if(sConnection.State != ConnectionState.Closed)
{
sConnection.Close();
}
}
}
And another function for counting the rows generated from the previous functions. But this function
Null Reference Exception or Object reference not set to an instance of object..
Can anyone help me in this... why it is catching error only for the functions above and working fine for all other similar functions.
private void UpdateLabelText()
{
SqlConnectionStringBuilder objConnectionString = new SqlConnectionStringBuilder();
objConnectionString.DataSource = txtHost.Text;
objConnectionString.UserID = txtUsername.Text;
objConnectionString.Password = txtPassword.Text;
objConnectionString.InitialCatalog = Convert.ToString(cmbDatabases.SelectedValue);
SqlConnection sConnection = new SqlConnection(objConnectionString.ConnectionString);
//To Open the connection.
sConnection.Open();
try
{
int SelectedCellTotal = 0;
int counter;
// Iterate through the SelectedCells collection and sum up the values.
for(counter = 0;counter < (dgResultView.SelectedCells.Count);counter++)
{
if(dgResultView.SelectedCells[counter].FormattedValueType == Type.GetType("System.String"))
{
string value = null;
// If the cell contains a value that has not been commited,
if(dgResultView.IsCurrentCellDirty == true)
{
value = dgResultView.SelectedCells[counter].EditedFormattedValue.ToString();
}
else
{
value = dgResultView.SelectedCells[counter].FormattedValue.ToString();
}
if(value != null)
{
// Ignore cells in the Description column.
if(dgResultView.SelectedCells[counter].ColumnIndex != dgResultView.Columns["TABLE_NAME"].Index)
{
if(value.Length != 0)
{
SelectedCellTotal += int.Parse(value);
}
}
}
}
}
// Set the labels to reflect the current state of the DataGridView.
lblDisplay.Text = "There are Total " + dgResultView.RowCount + cmbOperations.SelectedItem.ToString();
}
catch(Exception ex)
{
//All the exceptions are handled and written in the EventLog.
EventLog log = new EventLog("Application");
log.Source = "MFDBAnalyser";
log.WriteEntry(ex.Message);
}
finally
{
//If connection is not closed then close the connection
if(sConnection.State != ConnectionState.Closed)
{
sConnection.Close();
}
}
}
Also the lblDisplay.Text is not taking proper spaces.
Waiting for reply
OK, I don't really have an answer why you're getting a "null reference exception" - but a few points to throw in, nonetheless:
I would use sys.tables
instead of sysobjects
and having to specify what type of object to query for
ALWAYS put your disposable SqlConnection
and SqlCommand
into using(.....) { ...... }
blocks. That way, you won't need any finally {..}
blocks, and .NET will take care of properly disposing of those objects when they're no longer needed
why do you use a DataSet
when you only have a single table inside?? That's just unnecessary overhead - use a DataTable
instead!
don't open the SqlConnection
that early - wait 'til the very last moment, open it, execute query, close it again right away
actually, when using the SqlDataAdapter
, you don't need to open the SqlConnection
yourself at all - the SqlDataAdapter
will do that for you (and close it again after it is done reading the data)
do not mix the retrieval of the data from the database with the binding to the UI element - this is a very bad practice. From the GetTablesWithUpperCaseName
method, you should return something (like a DataTable
) to the caller (the UI) and let the UI handle the binding process
along the same lines: that method should not be grabbing stuff from UI elements (like text boxes) itself - pass in those values as method parameters, to get a cleaner code - one that you might actually be able to reuse in another project some day
This is how I think your first method ought to look like
public DataTable GetTablesWithUpperCaseName(string server, string database,
string username, string password)
{
// Create the datatable
DataTable dtListOfTablesWithUppercaseName = new DataTable("tableNames");
SqlConnectionStringBuilder objConnectionString = new SqlConnectionStringBuilder();
objConnectionString.DataSource = server;;
objConnectionString.UserID = username;
objConnectionString.Password = password;
objConnectionString.InitialCatalog = database;
// Define the Query against sys.tables - much easier and cleaner!
string selectTablesWithUppercaseName =
"SELECT NAME FROM sys.tables WHERE UPPER(name) COLLATE Latin1_General_BIN = name COLLATE Latin1_General_BIN AND is_msshipped = 0";
// put your SqlConnection and SqlCommand into using blocks!
using (SqlConnection sConnection = new SqlConnection(objConnectionString.ConnectionString))
using (SqlCommand sCommand = new SqlCommand(selectTablesWithUppercaseName, sConnection))
{
try
{
// Create the dataadapter object
SqlDataAdapter sDataAdapter = new SqlDataAdapter(selectTablesWithUppercaseName, sConnection);
// Fill the datatable - no need to open the connection, the SqlDataAdapter will do that all by itself
// (and also close it again after it is done)
sDataAdapter.Fill(dtListOfTablesWithUppercaseName);
}
catch (Exception ex)
{
//All the exceptions are handled and written in the EventLog.
EventLog log = new EventLog("Application");
log.Source = "MFDBAnalyser";
log.WriteEntry(ex.Message);
}
}
// return the data table to the caller
return dtListOfTablesWithUppercaseName;
}
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