How to Select a Value in an ASP.NET MVC5 @Html.DropDownListFor When the Value is in an Array?

In ASP.NET MVC5, use@html.dropdownListfor to process the array value as the selection of the drop -down table

In ASP.NET MVC 5, the

Auxiliary method is used to render the drop -down list for the attributes in the model. However, sometimes you may need to set the selection value of the drop -down list based on the value of the array or set in the model.

@Html.DropDownListFor() Consider the following example:

In this example,

<code class="language-csharp">@Html.DropDownListFor(m => m.Configurations[0].HelperCodeType, (SelectList)Model.HelperCodeTypeItems, new { id = "Configurations[0].HelperCodeType" })</code>

attribute is an array of

object. We hope to set the selection value of the drop -down list according to the Configurations attribute of the first element in the array. AggregationLevelConfiguration Configurations However, if we try to use the following code to set the selection value of the drop -down list: HelperCodeType

We will encounter errors. This is because the

constructor expects the fourth parameter is the string, but the

<code class="language-csharp">new SelectList(Model.HelperCodeTypeItems, "Id", "Name", Model.Configurations[0].HelperCodeType)</code>

attribute is byte type.

SelectList In order to solve this problem, we can use one of the following two methods: Model.Configurations[0].HelperCodeType

Method 1: Use Editortemplate

Create a custom for type. In , we can use the auxiliary method to render the drop -down list as the

attribute. We can also set the selection value of the drop -down list according to the attribute.

AggregationLevelConfiguration For example, set the selection value of the drop -down list below to EditorTemplate attributes of the EditorTemplate object: @Html.DropDownListFor() HelperCodeType Model.HelperCodeType Method 2: Generate a new SELECTList

EditorTemplate In this method, we will generate a new Model object for each element in the HelperCodeType array. Then, we can set the selection value of the drop -down list according to the current element's

attribute.

<code class="language-csharp">@model yourAssembly.AggregationLevelConfiguration
@Html.DropDownListFor(m => m.HelperCodeType, (SelectList)ViewData["CodeTypeItems"])
.... // AggregationLevelConfiguration的其他属性</code>

For example, the following code will generate a new object for each element in the array in the array:

Both methods allow us to set the selection value of the drop -down list based on the value of the array or collection in the model. Configurations

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