duplicate validation at kendo grid with dropdown

Hello,

You need to check Condition 

if(rec.MiscellaneousReceipt.MItemId == data)

because data want this.value() want return MItemId. 

You need to use below code to get selected rows.

var rows = grid.select();
    var selectedIds = [];

    $(rows).each(function(){
      selectedIds.push($(this).attr("data-uid"))
    });

Now based on selectedIds you can get gridview rows and compare duplicate. 

Please refer kendo UI document for the same.

https://docs.telerik.com/kendo-ui/api/javascript/ui/grid/methods/select

Thanks

not working sir

modify this line

if(alreadyItemInGrid) {ShowErrorMessage("Item Exists")}

to

if(alreadyItemInGrid.length>0) {ShowErrorMessage("Item Exists")}

Please try below code. 

var alreadyItemInGrid = gridData.filter(function(rec) {
    return rec.MiscellaneousReceipt.MItemId == data; // Filter out the appropriate one
})[0];

if(alreadyItemInGrid != null) {
   ShowErrorMessage("Duplicate record found.");
}

Thanks