The 'Key expression is undefined' error occurs when you use GridViewExtension.BindToLINQ / GridViewExtension.BindToEF methods

• Aug 30, 2023

Error Description:

This error can occur when the GridViewExtension.BindToLINQ and GridViewExtension.BindToEF methods cannot automatically recognize the key (unique) column from the TableName or QueryableSource specified at runtime.

Solution:

Do the following to resolve this issue:

• Use the GridViewExtension.BindToLINQ / GridViewExtension.BindToEF methods (MVC).

• Specify the e.KeyExpression property.

• C#

@Html.DevExpress().GridView(  
    settings => {  
    ...  
}).BindToLINQ(string.Empty, string.Empty, (s, e) => {  
    ...  
    e.KeyExpression = UNIQUE_KEY_COLUMN_NAME;  
}).GetHtml()

• VB.NET

@Html.DevExpress().GridView( _  
    Sub(settings)  
        ...  
End Sub).BindToLINQ(String.Empty, String.Empty,  
New EventHandler(Of DevExpress.Data.Linq.LinqServerModeDataSourceSelectEventArgs)( _  
Sub(s, e)  
        ...  
        e.KeyExpression = UNIQUE_KEY_COLUMN_NAME  
End Sub)).GetHtml()