i'm having an error " Object reference not set to an instance of an object. "
// Define the ADO.NET objects.
SqlConnection con = new SqlConnection(connectionString);
string selectSQL = "SELECT * FROM tbl_lecturer_project";
SqlCommand cmd = new SqlCommand(selectSQL, con);
SqlDataAdapter adapter = new SqlDataAdapter(cmd);
DataSet dsPubs = new DataSet();
// Try to open database and read information.
try
{
con.Open();
adapter.Fill(dsPubs, "tbl_lecturer_project");
// This command is still linked to the data adapter.
cmd.CommandText = "SELECT * FROM tbl_student_project_choice";
adapter.Fill(dsPubs, "tbl_student_project_choice");
cmd.CommandText = "SELECT * FROM tbl_team";
adapter.Fill(dsPubs, "tbl_team");
DataRelation SCoiceLec = new DataRelation("SCoiceLec", dsPubs.Tables["tbl_lecturer_project"].Columns["lecturerProjectId"], dsPubs.Tables["student_project_choice"].Columns["choiceProjectId"]);
DataRelation SChoiceNTeam = new DataRelation("SChoiceNTeam",dsPubs.Tables["student_project_choice"].Columns["choiceGroupId"], dsPubs.Tables["tbl_team"].Columns["teamId"]);
please help. i want to retrieve data from all 3 tables.
There are a number of problems with your code. Here is one:
adapter.Fill(dsPubs, "tbl_lecturer_project");
should be
adapter.Fill(dsPubs);
I think what you want is this:
string selectSQL = #"SELECT * FROM tbl_lecturer_project;
SELECT * FROM tbl_student_project_choice;
SELECT * FROM tbl_team";
using(SqlConnection con = new SqlConnection(connectionString))
{
con.Open();
using(SqlCommand cmd = new SqlCommand(selectSQL, con))
{
using(SqlDataAdapter adapter = new SqlDataAdapter(cmd))
{
DataSet dsPubs = new DataSet();
adapter.Fill(dsPubs);
// use dataset.
}
}
}
The three tables will have the names Table, Table1, and Table2
Related
I am trying to make a feedback form where I want to show the name which is inserted n number of times.
My DataBase has for example 9 duplicate names as feedback was input for that same person 9 times and I want to display it on the result that common name.
Please help me out to complete the code/solution or Correct the code and get the result.
SQL QUERY IS RUNNING PROPERLY IT IS SELECTING THE SINGLE DATA FROM DATABASE BUT HOW TO SHOW THIS ON WEBPAGE
public void cal_F2name()
{
string oracledb = "Data Source=(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP****))(****))(CONNECT_DATA =(SERVER = DEDICATED)(SID = ORCL));";
OracleConnection conn = new OracleConnection(oracledb);
conn.Open();
OracleCommand cmd = new OracleCommand();
cmd.Connection = conn;
OracleDataAdapter da1 = new OracleDataAdapter();
DataTable dt1 = new DataTable();
DataSet ds1 = new DataSet();
cmd.CommandText = "SELECT DISTINCT (F2NAME) FROM CMDC_FEEDBACK WHERE PRG_NAME ='" + cb_prg_name.SelectedValue + "'";
da1.SelectCommand = cmd;
da1.Fill(ds1);
name = Convert.ToString(ds1.Tables[0].Rows[0][0].ToString());
Label58.Text = String.Format("{0:0.00}",name);
conn.Close();
}
try using below code, i have made some change in sql query to get only single record as result.
public void cal_F2name()
{
string oracledb = "Data Source=(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP****))(****))(CONNECT_DATA =(SERVER = DEDICATED)(SID = ORCL));";
OracleConnection conn = new OracleConnection(oracledb);
conn.Open();
OracleCommand cmd = new OracleCommand();
cmd.Connection = conn;
OracleDataAdapter da1 = new OracleDataAdapter();
DataTable dt1 = new DataTable();
DataSet ds1 = new DataSet();
cmd.CommandText = "SELECT max(DISTINCT (F2NAME)) FROM CMDC_FEEDBACK WHERE PRG_NAME ='" + cb_prg_name.SelectedValue + "' AND F2NAME<>'' AND F2NAME IS NOT NULL" ;
da1.SelectCommand = cmd;
da1.Fill(ds1);
name = Convert.ToString(ds1.Tables[0].Rows[0][0].ToString());
Label58.Text = String.Format("{0:0.00}",name);
conn.Close();
}
i have not check but it will work, if you result binding to lable is correct.
Right now this is my code, it only databinds the last mentioned table.
I have 2 tables the "Products" and "Phone", and I would like to databind both of them to the Listview1.
if (!IsPostBack)
{
ListView1.DataSource = this.GetDatatable2();
ListView1.DataSource = this.GetData();
ListView1.DataBind();
}
private DataSet GetData()
{
string conString = ConfigurationManager.ConnectionStrings["CARP"].ConnectionString;
string query = "SELECT * FROM Produtos WHERE Id= '" + Request.QueryString["Id"] + "'";
SqlCommand cmd = new SqlCommand(query);
using (SqlConnection con = new SqlConnection(conString))
{
using (SqlDataAdapter sda = new SqlDataAdapter())
{
cmd.Connection = con;
sda.SelectCommand = cmd;
using (DataSet ds = new DataSet())
{
sda.Fill(ds);
return ds;
}
}
}
}
private DataSet GetDatatable2()
{
string conString = ConfigurationManager.ConnectionStrings["CARP"].ConnectionString;
string query = "SELECT * FROM Phone WHERE Id= '" + Request.QueryString["Id"] + "'";
SqlCommand cmd = new SqlCommand(query);
using (SqlConnection con = new SqlConnection(conString))
{
using (SqlDataAdapter sda = new SqlDataAdapter())
{
cmd.Connection = con;
sda.SelectCommand = cmd;
using (DataSet ds = new DataSet())
{
sda.Fill(ds);
return ds;
}
}
}
}
The reason why it only binds the second table is, that you don't add the tables but set them as data source.
To add something you use the operator += instead of =.
But in this situation this doesn't seem appropriate. I think you should merge both tables at first. With databinding the ListView would generate the columns automatically. Therefore you would need the same column headers in both tables. Anything else isn't meaningful at all.
You could use a SQL UNION and select both tables in one query, too.
I am currently fetching a dataset from following query select * from TableName WHERE ColumnName ='values''s' query executes without any error and return dataset was empty rows. When i execute the same in SQL Worksheets it return data
Following code for ref.
string sqlQuery = "select * from TableName WHERE Name ='McNaught''s'";
SqlConnection conn = new SqlConnection(ConnectionString);
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = sqlQuery;
SqlDataAdapter adapter = new SqlDataAdapter();
adapter.SelectCommand = cmd;
DataSet ds = new DataSet();
conn.Open();
adapter.Fill(ds);
conn.Close();
Please try this:
string sqlQuery = 'SELECT * FROM TableName WHERE Name ="McNaught\'s"'
The Problem is you need to provide Escape Sequence before the second ' so that compiler can distinguish between the previous apostrophe. Try this.
string sqlQuery = "select * from TableName WHERE Name ='McNaught'\'s'";
SqlConnection conn = new SqlConnection(ConnectionString);
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = sqlQuery;
SqlDataAdapter adapter = new SqlDataAdapter();
adapter.SelectCommand = cmd;
DataSet ds = new DataSet();
conn.Open();
adapter.Fill(ds);
conn.Close();
Try this it will work with \ escape sequence.
string sqlQuery = "select * from TableName WHERE Name ='McNaught\"s'";
I'm using this video to try and populate results from a DataGridView, and am receiving the above error. The below code pertains to this error - I pass values into a stored procedure, then the final SELECT returns the values in the table in the DataGridView.
SqlConnection con = new SqlConnection();
con.ConnectionString = "integrated security=SSPI;data source=SERV;" + "persist security info=False;initial catalog=DB";
con.Open();
SqlCommand select = new SqlCommand("SELECT * FROM Table");
SqlCommand enter = new SqlCommand("sp_Proc", con);
// Stored Procedure
enter.CommandType = CommandType.StoredProcedure;
enter.Parameters.Add(new SqlParameter("#vvalue", SqlDbType.VarChar)).Value = Convert.ToString(txt1.Text);
enter.Parameters.Add(new SqlParameter("#dvalue", SqlDbType.Decimal)).Value = Convert.ToDecimal(txt2.Text);
enter.ExecuteNonQuery();
// DataGrid returns the SELECT
SqlDataAdapter sadapt = new SqlDataAdapter(select);
sadapt.SelectCommand = select;
DataTable dtab = new DataTable();
sadapt.Fill(dtab); // generates the error
BindingSource b = new BindingSource();
b.DataSource = dtab;
dGrid.DataSource = b;
sadapt.Update(dtab);
con.Close();
You did not pass connection object on the command. Try this instead,
SqlCommand select = new SqlCommand("SELECT * FROM Table", con);
You are passing connection object to your enter command but didnt pass the connection object to your select command
SqlCommand select = new SqlCommand("SELECT * FROM Table");
SqlCommand enter = new SqlCommand("sp_Proc", con);
Use this
SqlCommand select = new SqlCommand("SELECT * FROM Table",con);
SqlCommand cmd = new SqlCommand("sp_StockAnalysis2") // connection missing in sqlcommand
SqlCommand cmd = new SqlCommand("sp_StockAnalysis2",Connection())// pass connection
I've looked through the other questions related to this, but I'm having a different issue. I can't get a specific item to return, it only returns my column name. How do I get the item to return?
public static string GetOneFieldRecord(string field, string companyNum)
{
DataSet ds = new DataSet();
SqlCommand comm = new SqlCommand();
string strSQL = "SELECT #FieldName FROM Companies WHERE CompanyNum = #CompanyNum";
SqlConnection conn = new SqlConnection();
conn.ConnectionString = #connstring;
comm.Connection = conn;
comm.CommandText = strSQL;
comm.Parameters.AddWithValue("#FieldName", field);
comm.Parameters.AddWithValue("#CompanyNum", companyNum);
SqlDataAdapter da = new SqlDataAdapter();
da.SelectCommand = comm;
conn.Open();
da.Fill(ds, "CompanyInfo");
conn.Close();
return ds.Tables[0].Rows[0].ItemArray[0].ToString();
}
I've also tried
return ds.Tables[0].Rows[0][0].ToString();
I'm just getting whatever is in the field variable.
If I pass in ("CompanyName", 33), it returns "CompanyName".
Your query (in sql profiler) is
SELECT 'CompanyName' FROM Сompanies WHERE СompanyNum = 33
So it returns exactly "CompanyName" string. You cannot pass column name as sqlparameter. You should do something like
public static string GetOneFieldRecord(string field, string companyNum)
{
DataSet ds = new DataSet();
SqlCommand comm = new SqlCommand();
string strSQL = string.Format("SELECT {0} FROM Companies WHERE CompanyNum = #CompanyNum", field);
SqlConnection conn = new SqlConnection();
conn.ConnectionString = #connstring;
comm.Connection = conn;
comm.CommandText = strSQL;
comm.Parameters.AddWithValue("#FieldName", field);
comm.Parameters.AddWithValue("#CompanyNum", companyNum);
SqlDataAdapter da = new SqlDataAdapter();
da.SelectCommand = comm;
conn.Open();
da.Fill(ds, "CompanyInfo");
conn.Close();
return ds.Tables[0].Rows[0].ItemArray[0].ToString();
}
But this code can be used for SQL injection.
To avoid Sql injection, you could check that fieldName in field variable is one of the table columns.
Or You could get SELECT * FROM Сompanies WHERE СompanyNum = #CompanyNum and get value of named column from datatable:
public static string GetOneFieldRecord(string field, string companyNum)
{
DataSet ds = new DataSet();
SqlCommand comm = new SqlCommand();
string strSQL = "SELECT * FROM Companies WHERE CompanyNum = #CompanyNum";
SqlConnection conn = new SqlConnection();
conn.ConnectionString = #connstring;
comm.Connection = conn;
comm.CommandText = strSQL;
comm.Parameters.AddWithValue("#FieldName", field);
comm.Parameters.AddWithValue("#CompanyNum", companyNum);
SqlDataAdapter da = new SqlDataAdapter();
da.SelectCommand = comm;
conn.Open();
da.Fill(ds, "CompanyInfo");
conn.Close();
return ds.Tables[0].Rows[0][field].ToString();
}