Error using the dropdown: The connection to the server has been lost

Question

I want to bind my comboBox through design but Visual Studio 2022 shows an error:

Microsoft Visual Studio

Error using the dropdown: The connection to the server has been lost.

Answer 1

Solution 1:

Whenever you are creating your project Select "Window Form App (.NET Framwork)". Then this error will never occure.

Reason: ADO.NET Entity Data Model are come up with .NET Framwork so if we want ADO.NET Entity Data Model then we have to choose "Window Form App (.NET Framwork)"

Solution 2: What if we have created our project without selecting "Window Form App (.NET Framwork)". Solution is to replace/add your App.config file with below code:

    <Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFramework>net6.0-windows</TargetFramework>
    <Nullable>enable</Nullable>
    <UseWindowsForms>true</UseWindowsForms>
    <ImplicitUsings>enable</ImplicitUsings>
      
      
  </PropertyGroup>

    <PropertyGroup>
        <OutputType>WinExe</OutputType>
        <TargetFramework>net48</TargetFramework>
        <Nullable>enable</Nullable>
        <UseWindowsForms>true</UseWindowsForms>
        <ImplicitUsings>enable</ImplicitUsings>
        <UseWPF>False</UseWPF>
        <PlatformTarget>AnyCPU</PlatformTarget>
    </PropertyGroup>
    <PropertyGroup>

        <LangVersion>10</LangVersion>
        <Nullable>enable</Nullable>
        <NullableContextOptions>enable</NullableContextOptions>
        <StartupObject></StartupObject>
        <PackAsTool>False</PackAsTool>
    </PropertyGroup>
    <ItemGroup>
        <Reference Include="System.Configuration" />
        <Reference Include="System.Data.DataSetExtensions" />
        <Reference Include="System.Net.Http" />
    </ItemGroup>
</Project>

In above code we just selected the target framework .NET