System.InvalidOperationException: 'The ConnectionString property has n

Ajay Bansode

The ConnectionString property has not been initialized.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: The ConnectionString property has not been initialized.

Source Error:

Line 43:                 cmd.Parameters.AddWithValue("@StudentName",txtName.Text);
Line 44:                 cmd.Parameters.AddWithValue("@Age",Convert.ToInt32(txtAge.Text));
Line 45:                 con.Open();
Line 46:                 int rows = cmd.ExecuteNonQuery();
Line 47:                 con.Close();

Source File: C:\Users\ajayb\source\repos\WebApplicationpract7c\WebApplicationpract7c\InsertDelete.aspx.cs Line: 45

2 Replies

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Amit Mohanty11mo ago

Accepted answer

Try this once:

int age;
if (!int.TryParse(txtAge.Text, out age))
{
    // Handle invalid input (show message, default to 0, etc.)
    Response.Write("Please enter a valid number for age.");
    return;
}

string connStr = "your-connection-string";
using (SqlConnection con = new SqlConnection(connStr))
{
    SqlCommand cmd = new SqlCommand(
        "INSERT INTO students (StudentName, Age) VALUES (@StudentName, @Age)", con);

    cmd.Parameters.Add("@Age", SqlDbType.Int).Value = age;
	cmd.Parameters.Add("@StudentName", SqlDbType.NVarChar, 100).Value = txtName.Text;

    con.Open();
    int rows = cmd.ExecuteNonQuery();
}

Tuhin Paul11mo ago

In your Web.config file (at the root of your project), add a section inside :

In your InsertDelete.aspx.cs file, do not hardcode or leave the connection empty. Instead, retrieve it from Web.config:

using System.Configuration; // Add this at the top

// Inside your method (e.g., button click handler)
string connectionString = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;

using (SqlConnection con = new SqlConnection(connectionString))
{
    using (SqlCommand cmd = new SqlCommand("INSERT INTO Students (StudentName, Age) VALUES (@StudentName, @Age)", con))
    {
        cmd.Parameters.AddWithValue("@StudentName", txtName.Text);
        cmd.Parameters.AddWithValue("@Age", Convert.ToInt32(txtAge.Text));

        con.Open();
        int rows = cmd.ExecuteNonQuery();
        // con.Close() is automatic due to 'using' block
    }
}

Security & Best Practices

Never hardcode connection strings in .cs files.
Always use parameterized queries (you’re already doing this ).
Use using blocks to auto-dispose connections and commands.
Validate user input before converting (e.g., check if txtAge.Text is a number)