How to solve an existence of XML namespace in WPF application?

An exception such as “WPF DataGrid (SfDataGrid) does not exist in the XML namespace” may occur when the Syncfusion assemblies referenced in the application do not match the application's target framework, or when different versions of Syncfusion assemblies are referenced within the same project.

Using same version of Syncfusion assembly in project to solve - Error:  Assembly 'X' uses 'Y' which has a higher version than referenced assembly ‘Y'

You can verify the version information by checking the properties of the referenced assemblies, as shown below:

Otherwise,

Error CS1705 Assembly 'X' uses 'Y' which has a higher version than referenced assembly ‘Y'

Using Syncfusion Assemblies Based on Target Framework to Resolve: “Control Does Not Exist in XML Namespace”

If you are developing an application targeting the .NET Framework 4.5.1, you must use the corresponding version of the Syncfusion assemblies that are built for that framework. You can identify the framework compatibility from the Syncfusion assembly version. For example:

• Version 14.4451.0.15 – Can be used in applications targeting .NET Framework 4.5.1

• Version 14.4450.0.15 – Can be used in applications targeting .NET Framework 4.5

• Version 14.4400.0.15 – Can be used in applications targeting .NET Framework 4.0

• Version 14.4350.0.15 – Can be used in applications targeting .NET Framework 3.5

As shown in the code screenshot below, ensure that the application's target framework and all referenced Syncfusion assemblies are aligned to the same framework version.