C# – LINQ Entity Framework sequence contains no elements

i have a database table that looks like this :

i am trying to retrieve the textboxValue with reference to the textboxID like this :

   public string GetPuzzle(string tid)
   {
       return context.crosswords.First(c => c.TextBoxID == tid).TextBoxValue;
   }

The above code ( CRUD class file ) gave me an error : System.InvalidOperationException: Sequence contains no elements

I have 100 text boxes created in a panel using 2 for loops , each text box have an id from 00-99 , so i am trying to append the textBoxValue to the text of the textboxes in the loop with reference to the textBoxID as the database above.

And the below code is how i try to do it , don't know if it is the correct way :

protected void Page_Load(object sender, EventArgs e)
{      
    for (int i = 0; i <= 9; i++)
    {           
        for (int j = 0; j <= 9; j++)
        {                
            TextBox tb = new TextBox();
            tb.MaxLength = (1);
            tb.Width = Unit.Pixel(40);
            tb.Height = Unit.Pixel(40);
            tb.ID = i.ToString() + j.ToString(); // giving each textbox a different id  00-99 
            Panel1.Controls.Add(tb);
            tb.Enabled = false;

            tb.Text = daoCrossword.GetPuzzle(tb.ID).ToString();
        } 

        Literal lc = new Literal();
        lc.Text = "<br />";
        Panel1.Controls.Add(lc);
    }
}

i am trying to select textboxvalue where textboxid = tid . tid will be my tb.ID in code behind and since there is 100 loops , every time tb.ID will increase from 00-99 , so when it reach an ID that contains a value in database , it will append the textboxvalue ( from database) to that textbox and so on .