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POobject reference not set to an instance of object exception when I try to add element to an array of type List<string>
 

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  1. POobject reference not set to an instance of object exception when I try to add element to an array of type List<string>
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    <p>In my project I've got a variable numtorust which represents the number of the toursits. (for testing purposes numtourist = 2)</p> <pre><code>for (i=0,numtoursut; i++) </code></pre> <p>I create dynamically 5 checkboxes with assigned checkedChanged event for each of tourist. Also to keep track which checkbox to which tourist applies I add attribute 'collection' </p> <pre><code>mycheckbox.InputAttributes.Add("collection", i.ToString()); </code></pre> <p>In checkedchanged event handler - when a user selects a checkbox I checked if its collection attribute is = 0 or 1 (first or second user). then I add checkbox value to <code>myche1</code> which is of type <code>List&lt;string)</code> if collection attribute = 1. </p> <p>But I when I decided to make one <strong>array</strong> of type <code>List&lt;string&gt;</code> with name <code>Toursit</code> when I try to add an element to it I got an exception - Object reference not set <strong>to an instance of object</strong> in this row of my code</p> <pre><code>Toursist[Int32.Parse(chk.InputAttributes["collection"])].Add(chk.InputAttributes["value"].ToString()); </code></pre> <p>Here is my full code</p> <pre><code> protected void checkChanged(object sender, EventArgs e) { CheckBox chk = (CheckBox)sender; /*that doesn't work if (chk.Checked) { Toursist[Int32.Parse(chk.InputAttributes["collection"])].Add(chk.InputAttributes["value"].ToString()); ((List&lt;String&gt;[])Session["chk"])[Int32.Parse(chk.InputAttributes["collection"])] = Toursist[Int32.Parse(chk.InputAttributes["collection"])]; }*/ //this works with myche1 of type list&lt;string&gt; if ((chk.Checked)&amp;&amp;(chk.InputAttributes["collection"].Equals("1"))) { myche1.Add(chk.InputAttributes["value"].ToString()); lblProba.Text += chk.InputAttributes["value"].ToString(); Session["chk1"] = myche1; } } </code></pre> <p>edit 1:</p> <p>teh new code of </p> <p>protected void checkChanged(object sender, EventArgs e) {</p> <pre><code>List&lt;string&gt;[] Toursist = new List&lt;string&gt;[2]; //Session["chk"] = new List&lt;string&gt;[2]; for (int i = 0; i &lt; Toursist.Length; i++) { Toursist[i] = new List&lt;string&gt;(); // ((List&lt;String&gt;[])Session["chk"])[i] = Toursist[i]; } CheckBox chk = (CheckBox)sender; if (chk.Checked) { if (((List&lt;String&gt;[])Session["chk"])[Int32.Parse(chk.InputAttributes["collection"])] == null) { ((List&lt;String&gt;[])Session["chk"])[Int32.Parse(chk.InputAttributes["collection"])] = Toursist[Int32.Parse(chk.InputAttributes["collection"])]; } Toursist[Int32.Parse(chk.InputAttributes["collection"])].Add(chk.InputAttributes["value"].ToString()); lblProba.Text += chk.InputAttributes["collection"].ToString(); ((List&lt;String&gt;[])Session["chk"])[Int32.Parse(chk.InputAttributes["collection"])] = Toursist[Int32.Parse(chk.InputAttributes["collection"])]; } </code></pre> <p>again the same mistake this time when I test if Sessio["chk"] == 0.</p> <p>but If I uncomment (so I no more have this mistake) </p> <pre><code>// ((List&lt;String&gt;[])Session["chk"])[i] = Toursist[i]; </code></pre> <p>on each postback event my session will be empty and I don't want!! </p>
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    1. PO
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      1. PTAnswer
    1. This table or related slice is empty.
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    1. USMilka Salkova
    1. USMilka Salkova
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    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
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      1. PTAnswer
    1. This table or related slice is empty.
    1. This table or related slice is empty.
 

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