Conditional IF in Grid Column in UI for Blazor

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Conditional IF in Grid Column

3 Answers 183 Views

Grid

This is a migrated thread and some comments may be shown as answers.

Richard asked on 06 Jun 2019, 07:50 AM

Hi all,

New to Blazor and Web development in General, but using Blazor as a way to bridge the gap between my c# knowledge and the web.

Just wondering if anyone has any knowledge of being able to do a if inside a Grid Column The end goal i'm trying to achieve is if a value is contained within the the property of the CurrentRecord then a button will appear binding to a function, if no record appears then the cell would remain empty.

this is the code i'm bodged together

<TelerikGrid data="@Histories" height="600px" Pageable="true" PageSize="20" Sortable="true" Filterable="true">
<TelerikGridColumns>
<TelerikGridColumn Field="Casecode" />
<TelerikGridColumn Field="Historytext" />
<TelerikGridColumn Field="Createdate" Title="Create Date" />
<TelerikGridColumn>
<Template>
@{
CurrentRecord = context as CaseHistory;
if(CurrentRecord.Blobid > 0)
{
<TelerikButton>Open</TelerikButton>
}
}
</Template>

</TelerikGridColumn>
</TelerikGridColumns>
</TelerikGrid>

at the moment when i'm running the code the command brower is showing an error

Error: System.ArgumentNullException: Value cannot be null.
Parameter name: name
at System.Type.GetProperty(String name, BindingFlags bindingAttr)
at Telerik.Blazor.Components.Grid.TelerikGridFilterHeaderBase`1.get_PropInfo()
at Telerik.Blazor.Components.Grid.TelerikGridFilterHeaderBase`1.get_PropType()
at Telerik.Blazor.Components.Grid.TelerikGridFilterHeaderBase`1.get_PropTypeName()
at Telerik.Blazor.Components.Grid.TelerikGridFilterHeaderBase`1.ResetFilterText()
at Telerik.Blazor.Components.Grid.TelerikGridFilterHeaderBase`1.OnInit()
at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()

any help to point me in a direction would help.

Thanks

Richard

3 Answers, 1 is accepted

answered on 06 Jun 2019, 10:07 AM

Fixed the issue after taking a break from looking at it.

i had to Bind the column to the property, before using the template to check if the data existed which showed the button.

<TelerikGrid data="@Histories" height="600px" Pageable="true" PageSize="20" Sortable="true" Filterable="true">
<TelerikGridColumns>
<TelerikGridColumn Field="Casecode" />
<TelerikGridColumn Field="Historytext" />
<TelerikGridColumn Field="Createdate" Title="Create Date" />
<TelerikGridColumn Field="Blobid">
<Template>
@{
CurrentRecord = context as CaseHistory;
if(CurrentRecord.Blobid >= 1)
{
<TelerikButton>Open</TelerikButton>
}
}
</Template>

</TelerikGridColumn>
</TelerikGridColumns>
</TelerikGrid>

Accepted

answered on 06 Jun 2019, 10:58 AM

Hi Richard,

As you just found (I almost sent this before seeing your post), a Field is required at the moment. If the actual model does not have a field for every templated column, you could use a view model that inherits the actual model and adds fields for all columns that are needed.

Below is an example how you can do this without a field (I highlighted the key changes):

I use a local variable in the template to prevent it from keeping old values in the global scope. I recommend you take this approach in any case.
I disabled filtering on that column, because it does not have a Field, so it could not be filtered.

I am also logging this exception for fixing, if the column does not have a field, it should not throw, but simply not be filterable/sortable/... and you can track its status by clicking the Follow button here: https://feedback.telerik.com/blazor/1412128-filterable-column-without-field-throws-a-null-exception.

@using Telerik.Blazor.Components.Grid

@using Telerik.Blazor.Components.Button

<TelerikGrid data="@Histories" height="600px" Pageable="true" PageSize="20" Sortable="true" Filterable="true">

<TelerikGridColumns>

<TelerikGridColumn Field="Casecode" />

<TelerikGridColumn Field="Historytext" />

<TelerikGridColumn Field="Createdate" Title="Create Date" />

<TelerikGridColumn Filterable="false">

<Template>

@{

var CurrentRecord = context as CaseHistory;

if (CurrentRecord.Blobid > 0)

{

<TelerikButton OnClick="@(() => MyCustomCommand(CurrentRecord))">Open</TelerikButton>

}

</Template>

</TelerikGridColumn>

</TelerikGridColumns>

</TelerikGrid>

@result

@functions {

public class CaseHistory

{

public int Id { get; set; }

public int Casecode { get; set; }

public string Historytext { get; set; }

public DateTime Createdate { get; set; }

public int Blobid { get; set; }

}

IEnumerable<CaseHistory> Histories = Enumerable.Range(1, 50).Select(x => new CaseHistory

{

Id = x,

Casecode = x,

Historytext = "text " + x,

Createdate = DateTime.Now.AddDays(-x),

Blobid = (x % 3 == 0) ? x : -x

});

string result { get; set; }

void MyCustomCommand(CaseHistory itm)

{

result = $"custom command fired for {itm.Id} on {DateTime.Now}";

StateHasChanged();

}

Regards,
Marin Bratanov
Progress Telerik UI for Blazor