An unhandled exception of type 'System.InvalidOperationException' occurred in System.Data.dll While writing from textbox to sql server 2012

Question

Trying my first WPF textbox to SQL express connection. I am receiving a An unhandled exception of type 'System.InvalidOperationException' occurred in System.Data.dll While using sql 2012 express trying to write to a table called

EVUSERS

on database

Employee

The error comes at

connection.Open();

Here is my code.

void saveData()
        {
            try
            {
                string firstName = FNameTextbox.Text;

                string connectionString = @"Data Source=.\\SQLEXPRESS;  Database=Employee;Integrated Security=True;User Instance=True";
                using (SqlConnection connection = new SqlConnection(connectionString))
                {
                    using (SqlCommand command = connection.CreateCommand())
                    {
                        command.CommandText = " INSERT INTO EVUSERS (FName) VALUES (@FName)";

                        command.Parameters.AddWithValue("@FName", firstName);

                        connection.Open();
                        command.ExecuteNonQuery();
                        connection.Close();
                    }
                }
            }
            catch (SqlException ex)
            {
                MessageBox.Show(ex.Message);
            }         
       }

Here is an image of the table I am trying to insert the data into from the taxtbox. Employee.dbo.EVUSERS

EDIT Screenshot

I have no idea why there is an error at the open(); Would it be the connections string? or the command I am using? The table definetely exists.

Answer 1

您的连接字符串中的数据源中有两个反斜杠，但是已使用@开头了字符串，因此不需要转义反斜杠。

Answer 2

MSDN says

1. Cannot open a connection without specifying a data source or server. or
2. The connection is already open.

So check your connection string

 using (SqlConnection connection = new SqlConnection("Data Source=(local);Initial Catalog=Employee;Integrated Security=SSPI;"))
{
    connection.Open();
    SqlCommand command= connection.CreateCommand();
    command.CommandText = " INSERT INTO EVUSERS (FName) VALUES (@FName)";
    command.Parameters.AddWithValue("@FName", firstName);
    command.ExecuteNonQuery();
}