asp.net selecting a checkbox from the grid view

i am trying to get checkbox value ,using c# In grid view the datasourc开发者_运维知识库e is from oracle i have added the checkbox but the value is not coming please help me in checking the value of check box this is for selecting the candidate if the checkbox is selected the particular candidate name is selected and the candidate names are appended in a string

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loop thru each row of the gridview and check whether the checkbox is selected or not-

foreach(Gridviewrow gridrow in gridview.Rows) {

Checkbox check=(Checkbox)gridrow.findControl("check"); if(check.checked) { //Write logic here } }