CODEWITHSUNDEEP
c#mysqlwinformsexecutereader
Michael
Michael

Reputation: 202

C# write select from mysql to variable

I have a big problem with save variable from select in mysql.

I wrote the following code:

string connectionstring = @"****;userid=*****;
password=***;database=***";
cnn = new MySqlConnection(connectionstring);
cnn.Open();
MySqlDataReader reader = null;
string query_date = "SELECT computer_name from wp_users where user_login = @login";
MySqlCommand command2 = new MySqlCommand(query_date, cnn);
command2.Parameters.AddWithValue("@login", metroTextBox.Text);
reader = command2.ExecuteReader();
while (reader.Read())
{
   string ColumnName = (string)reader["computer_name"];
}
cnn.Close();

I tried a lot of commands like ExecuteReader , ExecuteNonQuery , ExecuteScalar. but none of them worked and I am getting the same error: enter image description here

Really don't know what is wrong here I searched a lot and didn't find a solution of any form. Please help.

EDIT 1

I just did how you wrote and i did this :

     string connectionstring = @"****;userid=*****;
        password=***;database=***";
        cnn = new MySqlConnection(connectionstring);
        cnn.Open();
        MySqlDataReader reader = null;
        string query_date = "SELECT computer_name from wp_users where user_login = @login";
        MySqlCommand command2 = new MySqlCommand(query_date, cnn);
        command2.Parameters.AddWithValue("@login", metroTextBox.Text);
        DataTable table = new DataTable("ResultTable");
            MySqlDataAdapter adapter = new MySqlDataAdapter(command2);
            adapter.Fill(table);

            // This is the important line
            string result = table.Rows[0].ToString();

            cnn.Close();

Its the same error as earlier but another place. What's going on here... just don't know. Additional information mean in english : The key is not present in the dictionary enter image description here

EDIT 2

The funniest is when i just try to update with code :

 string connectionstring = @"****;userid=*****;
    password=***;database=***";
    cnn = new MySqlConnection(connectionstring);
    cnn.Open();
    MySqlDataReader reader = null;
    string upd = "UPDATE w_users Set computer_name = CURRENT_DATE where user_login =  @login";
    MySqlCommand command2 = new MySqlCommand(upd, cnn);
    command2.Parameters.AddWithValue("@login", metroTextBox.Text);
    DataTable table = new DataTable("ResultTable");
    SqlDataAdapter adapter = new MySqlDataAdapter(command2);
    adapter.Fill(table);
    cnn.Close();

And this works fine without any errors just update my table... What's the point of it

EDIT 3

I jutr try used to ExecuteScalar() and still i have the same error : enter image description here

Upvotes: 0

Views: 337

Answers (3)

Michael
Michael

Reputation: 202

The solution is simple:

Updating mysql.data.dll to the newest version fixed it (https://dev.mysql.com/downloads/connector/net/6.9.html).

Upvotes: 1

Thomas Flinkow
Thomas Flinkow

Reputation: 5105

If you have the MySqlDataAdapter, try if the following code works for you:

string connectionstring = @"****;userid=*****;
password=***;database=***";
cnn = new MySqlConnection(connectionstring);
cnn.Open();

string query_date = "SELECT computer_name AS `computer_name` FROM wp_users WHERE user_login = @login";

MySqlCommand command2 = new MySqlCommand(query_date, cnn);
command2.Parameters.AddWithValue("@login", metroTextBox.Text);

DataTable table = new DataTable("ResultTable");
MySqlDataAdapter adapter = new MySqlDataAdapter(command2);
adapter.Fill(table);

// This is the important line
string result = table["computer_name"];

cnn.Close();

Upvotes: 0

ichselber
ichselber

Reputation: 11

This exception wants to tell you, that there is no matching key in your resultset. Keys are case sensitive. Have you tried to spell your column name with all uppercase letters: (string)reader["COMPUTER_NAME"]?

Databases tend to return the column names in uppercase, even though you selected the column name in lower case.

Upvotes: 0

Related Questions