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c# mysql unable to output query to a textbox

here is my code:
private void searchInDatabase()
{
MySqlConnection c = new MySqlConnection("datasource=localhost; username=root; password=123456; port=3306");
MySqlCommand mcd;
MySqlDataReader mdr;
String query;
try
{
c.Open();
query = "SELECT * FROM test.classmates WHERE first_name ='"+searchName.Text+"'";
mcd = new MySqlCommand(query, c);
mdr = mcd.ExecuteReader();
if(mdr.Read())
{
firstName.Text = mdr.GetString("first_name");
middleName.Text = mdr.GetString("middle_name");
lastName.Text = mdr.GetString("last_name");
age.Text = mdr.GetString("age");
}
else
{
MessageBox.Show("Result Not Found");
}
}
catch(Exception error)
{
MessageBox.Show("Error: "+error.Message);
}
finally
{
c.Close();
}
}
I would like to ask for a help if I have missed on anything or I am doing it wrong. If you have free time, I will much appreciate it if you will comment the perfect way to do I implement this problem: I want to get data from MySQL then put it in a textbox.

According to MSDN you need to pass the column number as parameter
public override string GetString(int i)
So try to pass the column number (starts from 0) of your column name. Assuming the first_name is the first column of your table then
firstName.Text = mdr.GetString(0);
UPDATE
Try to use MySqlConnectionStringBuilder
MySqlConnectionStringBuilder conn_string = new MySqlConnectionStringBuilder();
conn_string.Server = "serverip/localhost";
conn_string.UserID = "my_user";
conn_string.Password = "password";
conn_string.Database = "my_db";
MySqlConnection conn = new MySqlConnection(conn_string.ToString();

First of all look at this sample of connection string and change your connection string:
'Server=myServerAddress;Port=1234;Database=myDataBase;Uid=myUsername;Pwd=myPasswor;'
If connection is OK send erorr message or full exception.

executenonquery not working, no columns edited

I am trying to update my database. However when I print object that gets returned by ExecuteNonQuery() it says 0.
Here's my code:
try
{
using(dbConnection = new SqliteConnection(dbConnString))
{
dbConnection.Open();
using(dbCommand = dbConnection.CreateCommand())
{
dbCommand.CommandText = "UPDATE 'GameObject' SET 'LocationX' = #locX, 'LocationY' = #locY, 'LocationZ' = #locZ WHERE 'id' = #id";
dbCommand.Parameters.AddRange(new SqliteParameter[]
{
new SqliteParameter("#locX") { Value = x},
new SqliteParameter("#locY") { Value = y},
new SqliteParameter("#locZ") { Value = z},
new SqliteParameter("#id") {Value = id}
});
int i = dbCommand.ExecuteNonQuery();
Debug.Log(i);
}//end dbcommand
}//end dbconnection
}//end try
catch(Exception e)
{
Debug.Log(e);
}
I think it's because of my where clause, because when I add this clause to a select query, my variables won't get updated. I just can't find what's wrong with it.
select query:
try
{
using(dbConnection = new SqliteConnection(dbConnString))
{
dbConnection.Open();
using(dbCommand = dbConnection.CreateCommand())
{
dbCommand.CommandText = "SELECT * FROM 'GameObject' WHERE 'id' = #id"; //without the where everything works fine
dbCommand.Parameters.Add (new SqliteParameter("#id") { Value = 1});
using(dbReader = dbCommand.ExecuteReader())
{
while(dbReader.Read())
{
id = dbReader.GetInt32(0);
x = dbReader.GetFloat(1);
y = dbReader.GetFloat(2);
z = dbReader.GetFloat(3);
}
}//end dbreader
}//end dbcommand
}//end dbconnection
_object.transform.position = new Vector3(x,y,z);
Debug.Log ("id: " + id + " location: " + _object.transform.position);
}
catch(Exception e)
{
Debug.Log(e);
}

One reason might be from https://www.sqlite.org/lang_keywords.html
For resilience when confronted with historical SQL statements, SQLite
will sometimes bend the quoting rules above:
If a keyword in single quotes (ex: 'key' or 'glob') is used in a
context where an identifier is allowed but where a string literal is
not allowed, then the token is understood to be an identifier instead
of a string literal.
Since none of them is keyword, try to use them without single quotes.

SQL Syntax Error (INSERT command)

I have a form with a text box and button, such that when the user clicks the button, the specified name in the text box is added to a table in my sql database. The code for the button is as follows:
private void btnAddDiaryItem_Click(object sender, EventArgs e)
{
try
{
string strNewDiaryItem = txtAddDiaryItem.Text;
if (strNewDiaryItem.Length == 0)
{
MessageBox.Show("You have not specified the name of a new Diary Item");
return;
}
string sqlText = "INSERT INTO tblDiaryTypes (DiaryType) VALUES = ('" + strNewDiaryItem + "');";
cSqlQuery cS = new cSqlQuery(sqlText, "non query");
PopulateInitialDiaryItems();
MessageBox.Show("New Diary Item added succesfully");
}
catch (Exception ex)
{
MessageBox.Show("Unhandled Error: " + ex.Message);
}
}
The class cSqlQuery is a simple class that executes various T-SQL actions for me and its code is as follows:
class cSqlQuery
{
public string cSqlStat;
public DataTable cQueryResults;
public int cScalarResult;
public cSqlQuery()
{
this.cSqlStat = "empty";
}
public cSqlQuery(string paramSqlStat, string paramMode)
{
this.cSqlStat = paramSqlStat;
string strConnection = BuildConnectionString();
SqlConnection linkToDB = new SqlConnection(strConnection);
if (paramMode == "non query")
{
linkToDB.Open();
SqlCommand sqlCom = new SqlCommand(paramSqlStat, linkToDB);
sqlCom.ExecuteNonQuery();
linkToDB.Close();
}
if (paramMode == "table")
{
using (linkToDB)
using (var adapter = new SqlDataAdapter(cSqlStat, linkToDB))
{
DataTable table = new DataTable();
adapter.Fill(table);
this.cQueryResults = table;
}
}
if (paramMode == "scalar")
{
linkToDB.Open();
SqlCommand sqlCom = new SqlCommand(paramSqlStat, linkToDB);
this.cScalarResult = (Int32)sqlCom.ExecuteScalar();
linkToDB.Close();
}
}
public cSqlQuery(SqlCommand paramSqlCom, string paramMode)
{
string strConnection = BuildConnectionString();
SqlConnection linkToDB = new SqlConnection(strConnection);
paramSqlCom.Connection = linkToDB;
if (paramMode == "table")
{
using (linkToDB)
using (var adapter = new SqlDataAdapter(paramSqlCom))
{
DataTable table = new DataTable();
adapter.Fill(table);
this.cQueryResults = table;
}
}
if (paramMode == "scalar")
{
linkToDB.Open();
paramSqlCom.Connection = linkToDB;
this.cScalarResult = (Int32)paramSqlCom.ExecuteScalar();
linkToDB.Close();
}
}
public string BuildConnectionString()
{
cConnectionString cCS = new cConnectionString();
return cCS.strConnect;
}
}
The class works well throughout my application so I don't think the error is in the class, but then I can't be sure.
When I click the button I get the following error message:
Incorrect syntax near =
Which is really annoying me, because when I run the exact same command in SQL Management Studio it works fine.
I'm sure I'm missing something rather simple, but after reading my code through many times, I'm struggling to see where I have gone wrong.

you have to remove = after values.
string sqlText = "INSERT INTO tblDiaryTypes (DiaryType) VALUES ('" + strNewDiaryItem + "');"
and try to use Parameterized queries to avoid Sql injection. use your code like this. Sql Parameters
string sqlText = "INSERT INTO tblDiaryTypes (DiaryType) VALUES (#DairyItem);"
YourCOmmandObj.Parameters.AddwithValue("#DairyItem",strNewDiaryIItem)

Remove the = after VALUES.

You do not need the =
A valid insert would look like
INSERT INTO table_name (column1, column2, column3,...)
VALUES (value1, value2, value3,...)
Source: http://www.w3schools.com/sql/sql_insert.asp

Please use following:
insert into <table name> Values (value);

Remove "=", and also i would recommend you to use string.format() instead of string concatenation.
sqlText = string.format(INSERT INTO tblDiaryTypes (DiaryType) VALUES ('{0}'), strNewDiaryItem);"

Input string was not in a correct format

I'm trying to make a simple application form were user can input data like 'reservationid', 'bookid', 'EmployeeID' and 'reservedate'. Its from my program Library System. 'reservationid' is an auto increment primary key while the rest are BigInt50, NVarChar50 and DateTime10 respectively. So I'm having this error: Input String was not in a correct format. It worked fine a while ago until I modified the 'reservationid' to auto increment so where did I go wrong? I've attached a sample of my code behind.
Any help would be greatly appreciated! Thanks in advance!
namespace LibraryManagementSystemC4.User
{
public partial class Reserving : System.Web.UI.Page
{
public string GetConnectionString()
{
return System.Configuration.ConfigurationManager.ConnectionStrings["LibrarySystemConnectionString"].ConnectionString;
}
//string reservationid
private void ExecuteInsert(string bookid, string EmployeeID, string reservedate)
{
SqlConnection conn = new SqlConnection(GetConnectionString());
string sql = "INSERT INTO BookReservation (reservationid, bookid, EmployeeID, reservedate) VALUES " + " (#reservationid, #bookid, #EmployeeID, #reservedate)";
try
{
conn.Open();
SqlCommand cmd = new SqlCommand(sql, conn);
SqlParameter[] param = new SqlParameter[3];
//param[0] = new SqlParameter("#reeservationid", SqlDbType.Int, 50);
param[0] = new SqlParameter("#bookid", SqlDbType.BigInt, 50);
param[1] = new SqlParameter("#EmployeeID", SqlDbType.NVarChar, 50);
param[2] = new SqlParameter("#reservedate", SqlDbType.DateTime, 10);
//param[0].Value = reservationid;
param[0].Value = bookid;
param[1].Value = EmployeeID;
param[2].Value = reservedate;
for (int i = 0; i < param.Length; i++)
{
cmd.Parameters.Add(param[i]);
}
cmd.CommandType = CommandType.Text;
cmd.ExecuteNonQuery();
}
catch (System.Data.SqlClient.SqlException ex)
{
string msg = "Insert error";
msg += ex.Message;
throw new Exception(msg);
}
finally
{
conn.Close();
}
}
protected void Page_Load(object sender, EventArgs e)
{
if (reservationidTextBox != null)
{
//reservationidTextBox.Text
ExecuteInsert(bookidTextBox.Text, EmployeeIDTextBox.Text, reservationidTextBox.Text);
ClearControls(Page);
}
else
{
Response.Write("Please input ISBN");
bookidTextBox.Focus();
}
{
//get bookid from Book Details and Employee PIN from current logged-in user
bookidTextBox.Text = DetailsView1.SelectedValue.ToString();
EmployeeIDTextBox.Text = HttpContext.Current.User.Identity.ToString();
}
}
public static void ClearControls(Control Parent)
{
if (Parent is TextBox)
{
(Parent as TextBox).Text = string.Empty;
}
else
{
foreach (Control c in Parent.Controls)
ClearControls(c);
}
}
}
}

If reservationid is auto incremented then remove it from your insert query
string sql = "INSERT INTO BookReservation ( bookid, EmployeeID, reservedate) VALUES (#bookid, #EmployeeID, #reservedate)";
also try
param[0].Value = Convert.ToInt64(bookid);
param[1].Value = EmployeeID;
param[2].Value = Convert.ToDate(reservedate);

after you made reservationid to autoincrement then you dont have to do like
string sql = "INSERT INTO BookReservation (reservationid, bookid, EmployeeID, reservedate) VALUES " + " (#reservationid, #bookid, #EmployeeID, #reservedate)";
remove reservationid to insert.
do like
string sql = "INSERT INTO BookReservation ( bookid, EmployeeID, reservedate) VALUES (#bookid, #EmployeeID, #reservedate)";

Its because you are not passing the reservationid an Integer value to your command parameters when it is not Auto Increment.
I can see from your code, that you have declared string reservationid, but you are not assigning it any value and secondly it should an integer value.

I know this is deeply necro-posted, but since it seems from Loupi's comment on 9Jun11 that he was still having problems, I'd post the actual answer. Bala's answer was what was still giving him the Input Type is not in a correct format error; using a Convert.ToInt64 statement in a value assignation was tripping it. Do the conversion in variables previous to assigning the parameter values and it works a charm. The most likely culprit is that bookid was some sort of non-zero empty string representation (blank quotes, a space, null, whatever).
Edit: A quick and easy one-line test that's relatively bulletproof:
long numAccountNum = Int64.TryParse(AccountNum, out numAccountNum) ? Convert.ToInt64(AccountNum) : 0;

What's wrong with my IF statement?

I'm creating an auditting table, and I have the easy Insert and Delete auditting methods done. I'm a bit stuck on the Update method - I need to be able to get the current values in the database, the new values in the query parameters, and compare the two so I can input the old values and changed values into a table in the database.
Here is my code:
protected void SqlDataSource1_Updating(object sender, SqlDataSourceCommandEventArgs e)
{
string[] fields = null;
string fieldsstring = null;
string fieldID = e.Command.Parameters[5].Value.ToString();
System.Security.Principal. WindowsPrincipal p = System.Threading.Thread.CurrentPrincipal as System.Security.Principal.WindowsPrincipal;
string[] namearray = p.Identity.Name.Split('\\');
string name = namearray[1];
string queryStringupdatecheck = "SELECT VAXCode, Reference, CostCentre, Department, ReportingCategory FROM NominalCode WHERE ID = #ID";
string queryString = "INSERT INTO Audit (source, action, itemID, item, userid, timestamp) VALUES (#source, #action, #itemID, #item, #userid, #timestamp)";
using (SqlConnection connection = new SqlConnection("con string = deleted for privacy"))
{
SqlCommand commandCheck = new SqlCommand(queryStringupdatecheck, connection);
commandCheck.Parameters.AddWithValue("#ID", fieldID);
connection.Open();
SqlDataReader reader = commandCheck.ExecuteReader();
while (reader.Read())
{
for (int i = 0; i < reader.FieldCount - 1; i++)
{
if (reader[i].ToString() != e.Command.Parameters[i].Value.ToString())
{
fields[i] = e.Command.Parameters[i].Value.ToString() + "Old value: " + reader[i].ToString();
}
else
{
}
}
}
fieldsstring = String.Join(",", fields);
reader.Close();
SqlCommand command = new SqlCommand(queryString, connection);
command.Parameters.AddWithValue("#source", "Nominal");
command.Parameters.AddWithValue("#action", "Update");
command.Parameters.AddWithValue("#itemID", fieldID);
command.Parameters.AddWithValue("#item", fieldsstring);
command.Parameters.AddWithValue("#userid", name);
command.Parameters.AddWithValue("#timestamp", DateTime.Now);
try
{
command.ExecuteNonQuery();
}
catch (Exception x)
{
Response.Write(x);
}
finally
{
connection.Close();
}
}
}
The issue I'm having is that the fields[] array is ALWAYS null. Even though the VS debug window shows that the e.Command.Parameter.Value[i] and the reader[i] are different, the fields variable seems like it's never input into.
Thanks

You never set your fields[] to anything else than null, so it is null when you are trying to access it. You need to create the array before you can assign values to it. Try:
SqlDataReader reader = commandCheck.ExecuteReader();
fields = new string[reader.FieldCount]

I don't really understand what your doing here, but if your auditing, why don't you just insert every change into your audit table along with a timestamp?

Do fields = new string[reader.FieldCount] so that you have an array to assign to. You're trying to write to null[0].