how to check if value exists in database from textbox c#

Lost User

It's easy:

commandText = "SELECT user from UserTable where id = @username"
SqlCommand command = new SqlCommand(commandText, connection);
command.Parameters.AddWithValue("@username", tbUser.Text);

OriginalGriff

It's not hard, it's easy - once you learn how to do it. Just to add to what Richard gave you, the whole code is along the lines of:

        using (SqlConnection con = new SqlConnection(strConnect))
            {
            con.Open();
            using (SqlCommand cmd = new SqlCommand("SELECT Age, Description FROM myTable WHERE ID = @ID", con))
                {
                cmd.Parameters.AddWithValue("@ID", myTextBox.Text);
                using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                    while (reader.Read())
                        {
                        int age = (int) reader\["Age"\];
                        string desc = (string) reader\["Description"\];
                        Console.WriteLine($"{age}\\n{desc}");
                        }
                    }
                }
            }

"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony AntiTwitter: @DalekDave is now a follower!

realJSOP

Answering a question like this is harder.

".45 ACP - because shooting twice is just silly" - JSOP, 2010
-----
You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
-----
When you pry the gun from my cold dead hands, be careful - the barrel will be very hot. - JSOP, 2013

Hailu Worku Obsse

Step one: Add new LINQ to SQL item from project Item in to your project and call it DXD (or any convinient name you like) Step two: drag and Drop the Employee TABLE from Server Explorer in your IDE to your LINQ to SQL DataContext object. Step Three: Add data source by selecting Object as data source Step Four: Go to your form and drag and drop Salary field from your data source object to your form Step Five: Set the Data Source of your EmployeeDatabinding object as EmployeeDatabinding.DataSource = DXD.Employee ... it is too long try another approach

Pete OHanlon

And what happens if the database is not SQL Server? What if the textbox is an ASP.NET Core one? You are making a lot of assumptions with your answer.

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F ES Sitecore

"SELECT"? He didn't say it was a SQL based database. You're making a lot of assumptions here ;)

Lost User

Pete O'Hanlon wrote:

And what happens if the database is not SQL Server? What if the textbox is an ASP.NET Core one? You are making a lot of assumptions with your answer.

Same can be said from OG's answer, which I still find very valuable. The assumption for SQL Server is a valid one; if it is another database a similar technique is used and the example given remains valid with minimal change. I'd argue that it should program against the interface, and use the CreateCommand method from the connection, taking the value of the textbox as an argument.

using (SqlConnection con = new SqlConnection(strConnect))
using (IDbCommand cmd = con.CreateCommand())
{
cmd.CommandText = "bla";
con.Open(); // as late as possible

And yes, even that would be improved by using the DBProviderFactory, getting the connectionstring and provider from the Settings.

Bastard Programmer from Hell :suss: If you can't read my code, try converting it here[^] "If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.

Pete OHanlon

This is true. It could be a find for all I know. Well spotted.

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realJSOP

There are as many ways to do this as there are people answering this question. Most of them depend on what mechanism you're using to access your database - Entity Framework - ADO - LINQ to SQL, or whatever. I personally prefer ADO, and I've written a reasonably generic DAL object to do it. Generic DAL using ADO[^] It can process stored proc calls or straight-up queries, and can map the returned data set to any object. Beyond that, your question is so vague that there's nothing more I can suggest

".45 ACP - because shooting twice is just silly" - JSOP, 2010
-----
You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
-----
When you pry the gun from my cold dead hands, be careful - the barrel will be very hot. - JSOP, 2013

Lost User

How big is the "database" (table)? Sometimes, it's simply more efficient to load the entire table into memory and reference it (i.e. for "look-ups") during data entry. No fancy querying required.

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it. ― Confucian Analects: Rules of Confucius about his food

Shraddha_Patel

private void CheckContactNumber() { string checkContactNum = "SELECT COUNT(*) FROM Employee WHERE ContactNumber = " + addContactNum.Text + " "; //01234567890 OleDbCommand cmd = new OleDbCommand(checkContactNum, conn); conn.Open(); OleDbDataReader dr = cmd.ExecuteReader(); //if (dr.Read() && addContactNum.Text != "") if (dr.Read()) { int count = (int)dr[0]; if(count>0) { err += "Contact number is already listed in the database\r\n"; errorContactNum.Visible = true; uniqueContactNumber = false; } } conn.Close(); }

Roland Skeyhill

t's not hard, it's easy - once you learn how to do it. Just to add to what Richard gave you, the whole code is along the lines of:

using (SqlConnection con = new SqlConnection(strConnect))
{
con.Open();
using (SqlCommand cmd = new SqlCommand("SELECT Age, Description FROM myTable WHERE ID = @ID", con))
{
cmd.Parameters.AddWithValue("@ID", myTextBox.Text);
using (SqlDataReader reader = cmd.ExecuteReader())
{
while (reader.Read())
{
int age = (int) reader["Age"];
string desc = (string) reader["Description"];
Console.WriteLine($"{age}\n{desc}");
}
}
}
}

:laugh: :cool: