I am trying to retrieve all names that was saved at the sql database
then suddenly I got the
nullreferenceexception was unhandled on filling up array - Object
reference not set to an instance of an object.
this was my code:
I got the error at the
imgName[i] = Convert.ToString(dt.Rows[i]["FinalImageName"]);
in that part, I'd like to fill imgName array all the name
how could i fix it?, help please
string c_string = "server=.\\sqlexpress;database=Blue;trusted_connection=true";
public static string ImageToShow;
private int NumOfFiles;
private string[] imgName;
SqlConnection c = new SqlConnection(c_string);
//SqlCommand cm = new SqlCommand(cmd,c);
private void frmMain_Load(object sender, EventArgs e) {
SqlConnection c = new SqlConnection(c_string);
try {
c.Open();
}
catch (SqlException ee) {
MessageBox.Show(ee.Message);
}
finally {
c.Close();
}
updateData();
}
private void updateData() {
SqlConnection c = new SqlConnection(c_string);
SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM FinalImages", c);
DataTable dt = new DataTable();
da.Fill(dt);
NumOfFiles = dt.Rows.Count;
for (int i = 0; i < dt.Rows.Count; i++) {
imgName[i] = Convert.ToString(dt.Rows[i]["FinalImageName"]);
}
}
You need to instantiate the imgName array .
private void updateData()
{
{
SqlConnection c = new SqlConnection(c_string);
SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM FinalImages", c);
DataTable dt = new DataTable();
da.Fill(dt);
NumOfFiles = dt.Rows.Count;
imgName = new string[NumOfFiles];
for (int i = 0; i < NumOfFiles; i++)
{
imgName[i] = Convert.ToString(dt.Rows[i]["FinalImageName"]);
}
}
}
That is because you have not specified the size of array... either specify size of array or use arraylist / generic list
Try this:
include namespace : using System.Collections.Generic;
string c_string = "server=.\\sqlexpress;database=Blue;trusted_connection=true";
public static string ImageToShow;
private int NumOfFiles;
//private string[] imgName;
List<string> imgName= new List<string>();
SqlConnection c = new SqlConnection(c_string);
//SqlCommand cm = new SqlCommand(cmd,c);
private void frmMain_Load(object sender, EventArgs e)
{
SqlConnection c = new SqlConnection(c_string);
try
{
c.Open();
}
catch (SqlException ee)
{
MessageBox.Show(ee.Message);
}
finally
{
c.Close();
}
updateData();
}
private void updateData()
{
SqlConnection c = new SqlConnection(c_string);
SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM FinalImages", c);
DataTable dt = new DataTable();
da.Fill(dt);
NumOfFiles = dt.Rows.Count;
for (int i = 0; i < dt.Rows.Count; i++)
{
// imgName[i] = Convert.ToString(dt.Rows[i]["FinalImageName"]);
imgName.Add(Convert.ToString(dt.Rows[i]["FinalImageName"]));
}
}
You haven't created an array, you have only created the variable that can hold the reference to the array.
Create the array once you know how many rows there are:
imgName = new string[dt.Rows.Count];
Related
I am working a project and i need to display on a form (frmCaterlogs) a list of items. I have successfully implimented a custom list using a user control & FlowLayOutPanel. However now i am stuck on how i can bind my caterlogs that sits on a sql database to my custom list: Here is my code. on the custome_list(CatList), i have 4 controls, Id, Titile, Description, Icon stored in database as binarydata in the sqldb. I am lost on how i can bind data to the custom list control that can look thought all the records in my database. Thanking you all in advace for your kind advices.
private void PopulateCatelog()// This code is triggered when frmcaterlogs loads.
{
int l;
string query = "SELECT * from ServicesCaterlogs";
SqlConnection con = new SqlConnection(cn);
SqlCommand cmd = new SqlCommand(query, con);
SqlDataAdapter sda = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
ListView Items = new ListView()
sda.Fill(dt);
l = dt.Rows.Count;
foreach(DataRow dr in dt.Rows) // This is where i am stuck
{
CatList iList = new CatList(dr["Item"].ToString());
iList.Title = dr;
}
CatList[] ListItem = new CatList[l];
//Loop though to check each item
for (int i = 0; i < ListItem.Length; i++)
{
ListItem[i] = new CatList();
ListItem[i].Title = fetch data for a list;
ListItem[i].Message = "fetch data for a lis";
ListItem[i].icon = Resources.Warning;
ListItem[i].IconBackground1 = Color.DarkGoldenrod;
if (FlowLayoutPanel.Controls.Count < 0)
{
FlowLayoutPanel.Controls.Clear();
}
else
{
FlowLayoutPanel.Controls.Add(ListItem[i]);
}
}
I got the desired result after altering the code as seen below
private void FrmCatalogs_Load(object sender, EventArgs e)
{
PopulateCatelog();
}
private void PopulateCatelog()
{
//Populate your listitem here
int l;
string query = "SELECT * from ServicesCaterlogs";
SqlConnection con = new SqlConnection(cn);
SqlCommand cmd = new SqlCommand(query, con);
SqlDataAdapter sda = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
sda.Fill(dt);
l = dt.Rows.Count;
foreach(DataRow dr in dt.Rows)
{
ListViewItem item = new ListViewItem(dr["Item"].ToString());
ListViewItem des = new ListViewItem(dr["Item_Description"].ToString());
CatList[] ListItem = new CatList[l];
for (int i = 0; i < ListItem.Length - l +1 ; i++)
{
ListItem[i] = new CatList();
ListItem[i].Title = item.Text;
ListItem[i].Message = des.Text;
ListItem[i].icon = Resources.Warning;
ListItem[i].IconBackground1 = Color.DarkGoldenrod;
if (FlowLayoutPanel.Controls.Count < 0)
{
FlowLayoutPanel.Controls.Clear();
}
else
{
FlowLayoutPanel.Controls.Add(ListItem[i]);
}
}
}
}
I have a table having 2 columns viz ID and DETAILS.Data in a table is like
id=01 details="pritam=123 sourav=263" like this
i am working on a windows for application ..when the application will run the output comes what i am going to tell.. 1.in my application one combobox is there.when the application will run all the id will be bind in a combobox from the table. 2.when user will choose any id suddenly the details column data will be shown in a datagrid view in a splitted format like this.
NAME KEY
PRITAM 123
SOURAV 263
in this data grid view user can delete ant row by selecting the and click on the below delete button. insert any row by clickng the add new row button at the end ,modify any existing data and finally click on the update button and all the data are going to be stored in that data base like in previous format.. for that i have written the code in c# like this..
namespace windows_csharpp
{
public partial class Form5 : Form
{
SqlConnection cc = new SqlConnection("Integrated Security=true;database=EDIXfer");
SqlDataAdapter da;
DataTable dt;
public Form5()
{
InitializeComponent();
}
private void Form5_Load(object sender, EventArgs e)
{
string sql="select EDIScheduleID from ETAProcessSchedule";
da= new SqlDataAdapter(sql, cc);
dt = new System.Data.DataTable();
da.Fill(dt);
for (int x = 0; x < dt.Rows.Count; x++)
{
comboBox1.Items.Add(dt.Rows[x][0].ToString());
}
}
ArrayList ls = new ArrayList();
int ss = 0;
int ss1 = 0;
int ssp = 1;
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
string sql = "select * from ETAProcessSchedule where EDIScheduleID='" + comboBox1.SelectedItem.ToString() + "'";
SqlDataAdapter adp = new SqlDataAdapter(sql, cc);
DataTable dt = new System.Data.DataTable();
adp.Fill(dt);
string stp = dt.Rows[0][21].ToString();
string[] stp1 = stp.Split(' ');
List<Class1> lst = new List<Class1>();
ls.Clear();
for (int x = 0; x < stp1.Length; x++)
{
ls.Add(stp1[x].ToString());
}
for (int x = 0; x < ls.Count; x++)
{
string ssttt = ls[x].ToString();
string[] sssp = ssttt.Split('=');
for (int x1 = 1; x1 < sssp.Length; x1++)
{
ss = 0;
ss1 = ssp;
Class1 cs = new Class1()
{
Value = sssp[ss], Key= sssp[x1].ToString()
};
lst.Add(cs);
}
}
dataGridView1.DataSource = lst;
}
private void Update_Click(object sender, EventArgs e)
{
string value = null;
string keys = null;
string query = null;
string str = null;
for (int i = 0; i < dataGridView1.Rows.Count; i++)
{
value = dataGridView1.Rows[i].Cells[0].Value.ToString();
keys = dataGridView1.Rows[i].Cells[1].Value.ToString();
string ss = value + '=' + keys;
str += ss + ' ';
}
query = "update ETAProcessSchedule set ProcParameters='"+str+"' where EDIScheduleID='"+comboBox1.SelectedItem.ToString()+"'";
da = new SqlDataAdapter(query, cc);
dt = new DataTable();
da.Fill(dt);
MessageBox.Show("Data Updated In Database Successfully");
}
and one class file is also there ..
class Class1
{
public string Value { get; set; }
public string Key { get; set; }
}
kindly help me in delete the selected row ,add the new row and update the all data in database like in previous format..
I think you already have working approach. If I understand right you need only two functions:
- Load Schedule details in the DataGridView (one key-value pair per row)
- Save edited/added/deleted key-value pairs to the database
Be sure next properties of DataGridView set to true:
this.YourDataGridView.AllowUserToAddRows = true;
this.YourDataGridView.AllowUserToDeleteRows = true;
And of course columns must be editable
In the methods was used const variables which was created in your Form (Form1)
private const string DETAILSDELIMITER = ' ';
private const string NAMEKEYDELIMITER = '=';
Method for loading schedule details in the DataGridView
//Use SqlParameters in the query,
//if not your application vulnerable for sql injection
private void LoadScheduleDetails(string scheduleID)
{
//You working only with one column, do not use '*' in SELECT statement if not nessesary
string query = "SELECT EDIScheduleID, ProcParameters FROM ETAProcessSchedule WHERE EDIScheduleID = #ScheduleID";
DataTable details = new DataTable();
//Get data from database
using (SqlConnection yourConnection = new SqlConnection(_YourConnectionString))
{
using(SqlCommand detailsCommand = new SqlCommand(query, yourConnection))
{
//Adding parameter
SqlParameter id = new SqlParameter { ParameterName = "#ScheduleID", SqlDbType = SqlDbType.NVarChar, Value = scheduleID };
detailsCommand.Parameters.Add(id);
using (SqlDataAdapter yourAdapter = new SqlDataAdapter(detailsCommand ))
{
yourAdapter.Fill(details);
}
}
}
this.YourDataGridView.Rows.Clear();
if (details.Rows.Count > 0)
{
DataRow temp = details.Rows[0];
//get column by name.
string[] pairs = temp.Field<String>("ProcParameters").Split(Form1.DETAILSDELIMITER);
//Adding rows manually without DataSource
foreach(string pair in pairs)
{
this.YourDataGridView.Rows.Add(pair.Split(Form1.NAMEKEYDELIMITER));
}
}
}
Method for saving data
I think better if you create columns already in the designer
Then you can access columns by it's name without hardcoding indexes
private void SaveDetails(string scheduleID)
{
StringBuilder details = new StringBuilder();
foreach(DataGridViewRow dgvr in this.YourDataGridView.Rows)
{
string name = dgvr.Cells[this.dgvColumn_Name.Name].Value.ToString();
string key = dgvr.Cells[this.dgvColumn_Key.Name].Value.ToString();
//Here you can check if values are ok(not empty or something else)
//Create pair
details.Append(Form1.DETAILSDELIMITER);
details.Append(name);
details.Append(Form1.NAMEKEYDELIMITER);
details.Append(key);
}
//remove first space character
if (details.Length > 0)
details.Remove(0, 1);
//Save data to database
string query = "UPDATE ETAProcessSchedule SET ProcParameters=#Details WHERE EDIScheduleID=#ScheduleID";
using (SqlConnection yourConnection = new SqlConnection(_YourConnectionString))
{
using (SqlCommand saveCommand = new SqlCommand(query, yourConnection))
{
//Adding parameters
SqlParameter id = new SqlParameter { ParameterName = "#ScheduleID", SqlDbType = SqlDbType.NVarChar, Value = scheduleID };
SqlParameter procParams = new SqlParameter { ParameterName = "#Details", SqlDbType = SqlDbType.NVarChar, Value = details.ToString() };
saveCommand.Parameters.Add(id);
saveCommand.Parameters.Add(procParams);
saveCommand.ExecuteNonQuery();
MessageBox.Show("Data Updated In Database Successfully");
}
}
}
Then use LoadScheduleDetails in the comboBox1_SelectedIndexChanged eventhandler
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
string scheduleID = comboBox1.SelectedItem.ToString();
if(String.IsNullOrEmpty(scheduleID) == false)
{
this.LoadScheduleDetails(scheduleID);
}
}
After data loaded, user can change it, add rows, delete rows
When user pressed "Update" button then use SaveDetails method,
where we collect data from all rows and update database with it
private void Update_Click(object sender, EventArgs e)
{
string scheduleID = comboBox1.SelectedItem.ToString();
if(String.IsNullOrEmpty(scheduleID) == false)
{
this.SaveDetails(scheduleID);
}
}
On your form load bind data:-
EDIT : -
private void Form5_Load(object sender, EventArgs e)
{
comboBox1.DataSource = loadddltable();
comboBox1.DisplayMember = "Name";
comboBox1.ValueMember = "ID";
}
public DataTable loadddl()
{
OleDbDataReader obj = null;
DataTable dt = new DataTable();
try
{
obj_dbconnection.CommandText = "Select * from TableName";
obj = obj_dbconnection.ExecuteReader();
if (obj != null)
{
if (obj.HasRows)
{
dt.Load(obj);
}
}
}
catch (Exception)
{
}
finally
{
if (obj != null)
{
obj.Close();
obj_dbconnection.Close();
}
}
return dt;
}
/*Code for Execute Reader*/
public OleDbDataReader ExecuteReader()
{
OleDbDataReader dr = null;
try
{
Open();
dr = cmd.ExecuteReader();
}
catch(Exception)
{ }
return dr;
}
/*Code for binding grid data*/
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
dataGridView1.DataSource= getDataForSelectedId(comboBox1.SelectedValue);
}
And then insert,edit,delete buttons as template fields to dataGridView and use dataGridView1_CellClick event to insert edit delete
I`m using this code to read from a sqlite table and add the row where it is to the DataGridview. The problem is that if I want to add the same item more than once, it will only add once. I want to be able to add as many items as I want.
private SQLiteConnection sql_con;
private SQLiteCommand sql_cmd;
private SQLiteDataAdapter DB;
private DataSet DS = new DataSet();
private DataTable DT = new DataTable();
private void btnAdicionaProduto_Click(object sender, EventArgs e)
{
string cmdInsereProdutos = "select codigo,Nome,Unidade,Valor from Produtos where codigo = #codigo";
InsereProdutosCaixa(cmdInsereProdutos);
if (dataGridViewProdutos.RowCount > 0)
{
dataGridViewProdutos.Columns[0].AutoSizeMode = DataGridViewAutoSizeColumnMode.AllCells;
dataGridViewProdutos.Columns[1].AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill;
dataGridViewProdutos.Columns[2].AutoSizeMode = DataGridViewAutoSizeColumnMode.AllCells;
dataGridViewProdutos.Columns[3].AutoSizeMode = DataGridViewAutoSizeColumnMode.AllCells;
for (int i = 0; i < dataGridViewProdutos.Columns.Count; i++)
{
int colw = dataGridViewProdutos.Columns[i].Width;
dataGridViewProdutos.Columns[i].AutoSizeMode = DataGridViewAutoSizeColumnMode.None;
dataGridViewProdutos.Columns[i].Width = colw;
}
txtCodigo.Text = "";
txtCodigo.Focus();
}
}
private void InsereProdutosCaixa(string txtQuery)
{
try
{
SetConnection();
sql_con.Open();
sql_cmd = sql_con.CreateCommand();
sql_cmd.Parameters.AddWithValue("#codigo", txtCodigo.Text);
sql_cmd.CommandText = txtQuery;
SQLiteDataReader readerProduto = sql_cmd.ExecuteReader();
DT.Load(readerProduto);
dataGridViewProdutos.DataSource = DT;
sql_con.Close();
}
catch (SQLiteException e)
{
MessageBox.Show(e.ToString(), "ERRO");
}
}
At this line of code dr = dt.Rows[k]; I am getting the exception Object reference not set to an instance of an object. where I am going wrong?
public partial class EditEngClgList : Form
{
public EditEngClgList()
{
InitializeComponent();
try
{
acccon = new OleDbConnection(#"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=db1.mdb");
acccon.Open();
}
catch (Exception err)
{
MessageBox.Show("Error:" + err);
}
string sql = "Select * From EngColeges order by EngClgID";
da = new OleDbDataAdapter(sql, acccon);
cmdb = new OleDbCommandBuilder(da);
dt1 = new DataTable();
da.Fill(dt1);
bs = new BindingSource();
bs.DataSource = dt1;
dataGridView1.DataSource = bs;
dataGridView1.Columns[1].Visible = false;
}
private void button4_Click(object sender, EventArgs e)
{
List<int> checkedclg = new List<int>();
DataRow dr;
List<int> checkedclgid = new List<int>();
for (int i = 0; i <= dataGridView1.RowCount - 1; i++)
{
if (Convert.ToBoolean(dataGridView1.Rows[i].Cells["Delete"].Value) == true)
{
checkedclg.Add(i);
checkedclgid.Add(Convert.ToInt16(dataGridView1.Rows[i].Cells["Delete"].Value));
}
}
foreach (int k in checkedclg)
{
dr = dt.Rows[k]; //this datatable object I hae created in another function
dt.Rows[k].Delete();
foreach (int j in checkedclgid)
{
OleDbCommand oleDbCommand = new OleDbCommand("DELETE FROM EngColeges WHERE EngClgID = #clgID", acccon);
oleDbCommand.Parameters.Add("#clgID", OleDbType.Integer).Value = j;
oleDbCommand.Prepare();
oleDbCommand.ExecuteNonQuery();
}
}
}
Thanks for any help
Place a breakpoint on that line - most likely the dt object is null.
To address the comment that k may be larger than Rows.Count, I would think if the problem was with k, you'd get an exception indicating the index is out of bounds (IndexOutOfBoundsException).
I have a datagrid view and it's datasource is MS Access(which have a datatype, currency, date/time, and numbers), It shows data in the database but doesn't show other data types, only words or any string, here is my code for adding rows
string[] rowData = new string[columnCount];
while (dr.Read())
{
for (int k = 0; k < columnCount; k++)
{
if (dr.GetFieldType(k).ToString() == "System.int32")
{
rowData[k] = dr.GetInt32(k).ToString();
}
if (dr.GetFieldType(k).ToString() == "System.String")
{
rowData[k] = dr.GetString(k);
}
}
dataGridView1.Rows.Add(rowData);
}
can you help me with this? thanks
Instead of using the code above, I use this code, and it works
private void Form6_Load(object sender, EventArgs e)
{
loadData();
}
private void loadData()
{
str = new OleDbConnectionStringBuilder();
str.Provider = "Microsoft.ace.Oledb.12.0";
str.DataSource = #"\\sisc-erelim\4_Printing\VTDB\DB\VirginiTEADB2.accdb";
con = new OleDbConnection(str.ConnectionString);
dataGridView1.DataSource = fillTable("Select* from Accountstbl");
dataGridView1.Columns["Password"].Visible = false;
dataGridView1.Columns["Picture"].Visible = false;
}
private DataTable fillTable(string sql)
{
DataTable datatable = new DataTable();
using (OleDbDataAdapter da = new OleDbDataAdapter(sql, con))
{
da.Fill(datatable);
}
return datatable;
}