I am using unity 2019.1 and I encountered a problem where any script I create cannot be added to a game object. It says that the class name could not be found even though the class name and script name are the same. Keep in mind that this is also a new script. I have some compiler errors but they are from temporary folders and I can run the game despite the compilers not being fixed.
Please post a script (using code tag).
You probably missing Monobehaviour.
I forgot to add the snapshots to the post
While first two screenshots are fine, third one presenting script should be posted using code tag.
See ** Using code tags properly .**
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class NewBehaviourScript : MonoBehaviour
{
// Start is called before the first frame update
void Start()
{
}
// Update is called once per frame
void Update()
{
}
}
Did you drag drop your new script onto Camera object yes?
Does it happens with any new script, as you created?
Does doble click on red error, navigates you anywhere?
Please copy paste full error here.
Did you try create new project again? Maybe current is corrupted somehow?
If so, do you have any previous version of Unity to try / test (i.e. 2018.3)?
Sorry, it is not obvious directly for me, what may be wrong. 
Yes i dragged and dropped the script to the camera object. It does not work with any other objects either. Any new script I create does not work and shows with the same error. It does not even work when I create a script component in the inspector. Double clicking the errors do not do anything. I have already tried creating a new project and the same problem occurs. I have also reinstalled unity several times, deleted my preferences, and used another version of unity 2019. I have no interest in using unity 2018 again.
This is the full error message:
Win32Exception: ApplicationName=‘C:\Users\TAN0212\Desktop\Unity\Editor\Data\Tools\RoslynScripts\unity_csc.bat’, CommandLine=‘/noconfig @ /UnityTempFile-6a5d5e019a364f4418f7a59be1b5beef’, CurrentDirectory=‘’, Native error= The system cannot find the file specified.
System.Diagnostics.Process.StartWithCreateProcess (System.Diagnostics.ProcessStartInfo startInfo) (at :0)
System.Diagnostics.Process.Start () (at :0)
(wrapper remoting-invoke-with-check) System.Diagnostics.Process.Start()
UnityEditor.Utils.Program.Start (System.EventHandler exitCallback) (at C:/buildslave/unity/build/Editor/Mono/Utils/Program.cs:44)
UnityEditor.Utils.Program.Start () (at C:/buildslave/unity/build/Editor/Mono/Utils/Program.cs:28)
UnityEditor.Scripting.Compilers.MicrosoftCSharpCompiler.StartCompilerImpl (System.Collections.Generic.List1[T] arguments, System.String argsPrefix) (at C:/buildslave/unity/build/Editor/Mono/Scripting/Compilers/MicrosoftCSharpCompiler.cs:106) UnityEditor.Scripting.Compilers.MicrosoftCSharpCompiler.StartCompiler () (at C:/buildslave/unity/build/Editor/Mono/Scripting/Compilers/MicrosoftCSharpCompiler.cs:141) UnityEditor.Scripting.Compilers.ScriptCompilerBase.BeginCompiling () (at C:/buildslave/unity/build/Editor/Mono/Scripting/Compilers/ScriptCompilerBase.cs:60) UnityEditor.Scripting.ScriptCompilation.CompilationTask.QueuePendingAssemblies () (at C:/buildslave/unity/build/Editor/Mono/Scripting/ScriptCompilation/CompilationTask.cs:286) UnityEditor.Scripting.ScriptCompilation.CompilationTask.Poll () (at C:/buildslave/unity/build/Editor/Mono/Scripting/ScriptCompilation/CompilationTask.cs:186) UnityEditor.Scripting.ScriptCompilation.EditorCompilation.CompileScriptAssemblies (UnityEditor.Scripting.ScriptCompilation.ScriptAssembly[ ] scriptAssemblies, UnityEditor.Scripting.ScriptCompilation.ScriptAssemblySettings scriptAssemblySettings, System.String tempBuildDirectory, UnityEditor.Scripting.ScriptCompilation.EditorScriptCompilationOptions options, UnityEditor.Scripting.ScriptCompilation.CompilationTaskOptions compilationTaskOptions, UnityEditor.Scripting.ScriptCompilation.EditorCompilation+CompileScriptAssembliesOptions compileScriptAssembliesOptions) (at C:/buildslave/unity/build/Editor/Mono/Scripting/ScriptCompilation/EditorCompilation.cs:1307) UnityEditor.Scripting.ScriptCompilation.EditorCompilation.CompileScripts (UnityEditor.Scripting.ScriptCompilation.ScriptAssemblySettings scriptAssemblySettings, System.String tempBuildDirectory, UnityEditor.Scripting.ScriptCompilation.EditorScriptCompilationOptions options, UnityEditor.Scripting.ScriptCompilation.EditorBuildRules+TargetAssembly[ ]& notCompiledTargetAssemblies, System.String[ ]& notCompiledScripts) (at C:/buildslave/unity/build/Editor/Mono/Scripting/ScriptCompilation/EditorCompilation.cs:1210) UnityEditor.Scripting.ScriptCompilation.EditorCompilation.CompileScripts (UnityEditor.Scripting.ScriptCompilation.EditorScriptCompilationOptions options, UnityEditor.BuildTargetGroup platformGroup, UnityEditor.BuildTarget platform) (at C:/buildslave/unity/build/Editor/Mono/Scripting/ScriptCompilation/EditorCompilation.cs:1102) UnityEditor.Scripting.ScriptCompilation.EditorCompilationInterface+<CompileScripts>c__AnonStorey3.<>m__0 () (at C:/buildslave/unity/build/Editor/Mono/Scripting/ScriptCompilation/EditorCompilationInterface.cs:288) UnityEditor.Scripting.ScriptCompilation.EditorCompilationInterface.EmitExceptionAsError[T] (System.Func1[TResult] func, T returnValue) (at C:/buildslave/unity/build/Editor/Mono/Scripting/ScriptCompilation/EditorCompilationInterface.cs:97)
UnityEditor.Scripting.ScriptCompilation.EditorCompilationInterface:CompileScripts(EditorScriptCompilationOptions, BuildTargetGroup, BuildTarget)
Still got no Idea sorry.
My only thoughts would be:
Try to load existing projects. Maybe from tutorials.
Could antivirus block something?
Try Report Bug, from Unity, and send project to team.
They do replay within few working days.
Maybe someone else got other idea.
Have you any other computer by any chance, to test on?
How do i get someone else to help?
I cannot report this bug because this is only happening on my computer
Once you submit bug, support may be able to assist with a solution.
Don’t forget attach your error and project.
There may be more cases like yours.
Guys how do you fix the problem. İ am get crazy from this problem reinstall 3, 4 version of Unity.