how to display a error message if values in database doesnot exists

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hi, i just created a database and created a table and tried to insert data into table using c# program, i written code for insert, update, delete.. but coming to delete code it works correctly...
the work is deleting the values if i enter the name in textbox and showing a message that "values deleted"... but actually i need is
when a name is entered which doesn't exists in table or database it should display a message that "values does not exists"...
the code i written is

C#

private void button3_Click(object sender, EventArgs e)
        {
            string name = textBox1.Text;
            string homephone = textBox2.Text;
            string workphone = textBox3.Text;
            string email = textBox4.Text;
            if (name == "")
            {
                MessageBox.Show("please enter name", "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            else
            {
                System.Data.SqlClient.SqlConnection sqlConnection3 =
new System.Data.SqlClient.SqlConnection("Persist Security Info=True;User ID=*****;Password=******;Initial Catalog=mydb5;Server=myserver");
                System.Data.SqlClient.SqlCommand cmd = new System.Data.SqlClient.SqlCommand();
                cmd.CommandType = System.Data.CommandType.Text;
                cmd.CommandText = "if exists (select * from phonebook) delete phonebook where NAME=@NAME;";
                cmd.Parameters.AddWithValue("@NAME", name);
                cmd.Parameters.AddWithValue("@HOMEPHONE", homephone);
                cmd.Parameters.AddWithValue("@WORKPHONE", workphone);
                cmd.Parameters.AddWithValue("@EMAIL", email);
                cmd.Connection = sqlConnection3;
                sqlConnection3.Open();
                cmd.ExecuteNonQuery();
                MessageBox.Show("values deleted");

            }
        }

additional information copied from non-solution below
hi mr.TADIT DASH.... your answer is good but what i need is a message should be displayed...

see...
when i type a name in textbox field... and click on delete.. it was showing values deleted even if the name does not exists in database....

when i type a name in textbox field... and click on delete.. it was showing deleted if the name exists in database.... and the values with the name were deleting,,,

my query is,,, when ever if i type a name which does not exist in database table... it should show "name doesnot exists in database"

please just check it once and answer me...

Posted 3-Jun-14 21:20pm

chaitanya556

Updated 3-Jun-14 22:58pm

Nelek

v3

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Comments

ridoy 4-Jun-14 4:07am

Then you should add search as like your insert or delete. Before deciding to delete you should make a search query with the textbox value to your database.

3 solutions

Solution 1

Before deleting a name 1st u select the data using where condition name;

then put the data in datatable

then

C#

 if(datatable.rows.count>0)
 {
    Your delete query 
 } 

 else
{
  your message;
}

Posted 3-Jun-14 21:53pm

murkalkiran

Comments

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ) 4-Jun-14 4:00am

Please read the question carefully. OP is not using any DataTable here.

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Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ) · Accepted Answer · 2014-06-03T22:05:00

Solution 2

To insert, you are using the below query...

C#

cmd.CommandText = "if exists (select * from phonebook) delete phonebook where NAME=@NAME;";

But before that, you want to check if that really exists or not. For that, you have to run another query to see if it exists or not. You can use COUNT().

C#

cmd.CommandText = "select count(someColumnName) from phonebook where NAME=@NAME;";

Now, use SqlDataReader or SqlAdapter or ExecuteScalar method to read the selected value. If that is > 0, then the name exists.

Note: Replace your existing Column Name for "someColumnName".

Posted 3-Jun-14 22:05pm

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ)

Updated 4-Jun-14 0:25am

v2

Comments

chaitanya556 4-Jun-14 4:59am

hi mr.TADIT DASH.... your answer is good but what i need is a message should be displayed...

see...
when i type a name in textbox field... and click on delete.. it was showing values deleted even if the name does not exists in database....

when i type a name in textbox field... and click on delete.. it was showing deleted if the name exists in database.... and the values with the name were deleting,,,

my query is,,, when ever if i type a name which does not exist in database table... it should show "name doesnot exists in database"

please just check it once and answer me...

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ) 4-Jun-14 6:21am

Hey,

I gave you the Logic so that you will get started. My intention was to get you started.

As I said "If that is > 0, then the name exists.". That means it does not exists, if it does not satisfies this, right... Just a matter of writing the codes, which I did not do for you. But DamithSL did it for you in Solution 4. However, the logic is same.

You accepted that answer, but you can also mark my solution as answer.

Thanks,
Tadit

Nelek 4-Jun-14 4:59am

OP wanted to chat with you using a non-solution. I have copied the information to the question before the solution 3 gets nuked, have a look

Nelek 4-Jun-14 5:01am

OK, OP did it correctly at the same time as me

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ) 4-Jun-14 6:24am

Thanks Nelek, :D

I am getting the notifications sometimes and sometimes not. As I notified for your reply, I saw that DamithSL posted an answer with the same logic :D :D and OP accepted that.

I was like, what !!! and OP replied me that it did not help him/her. :P :P

Regards,
Tadit

chaitanya556 4-Jun-14 6:38am

hey TADIT, i tried your logic.. actually i am new to this c# programming as i recently completed my course on .net.... so i just hooked up to some extent.. as i copy pasted mr.Damith's code and tyed my connection string it got success.. thats why i accepted his solution... you helped me alot.. thank you mr.TADIT..

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ) 4-Jun-14 6:41am

Hey, no issues... Thanks Navya. :)

DamithSL · Accepted Answer · 2014-06-03T23:12:00

get the count first and show the message if not exist, otherwise proceed with delete.. :-)

C#

using (SqlConnection cn = new SqlConnection(sqlConnectionString))
{
    cn.Open();

    using (SqlCommand commandRowCount
        = new SqlCommand("SELECT COUNT(*) FROM phonebook where NAME=@NAME", cn))
    {
        commandRowCount.Parameters.AddWithValue("@NAME", name);
        var countStart = (int)commandRowCount.ExecuteScalar();

        if(countStart< 1)
        {
            MessageBox.Show("Name doesnot exists in database");
            return;
        }
    }
    using (SqlCommand cmdDel
        = new SqlCommand("delete phonebook where NAME=@NAME", cn))
    {
        cmdDel.Parameters.AddWithValue("@NAME", name);
        cmdDel.ExecuteNonQuery();
        MessageBox.Show("values deleted");
    }
}