A ref or out argument must be an assignable variable

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I'm Calling a stored procedure for password change. But it is giving me Error.

What I have tried:

And On Button Click My Function is:-

C#

protected void BtnSave_Click(object sender, EventArgs e)
  {
      using (SampleDataContext dbContext = new SampleDataContext())
      {
          System.Nullable<char> outpt = null;
          System.Nullable<long> id = Convert.ToInt64(Session["USERID"]);
          dbContext.passwrdchange(id, old.Text.ToString().Trim(), newpass.Text.ToString().Trim(),ref outpt);

          if(outpt.ToString()=="T")
          {
              ClientScript.RegisterStartupScript(this.GetType(), "SuccessMsg", "<script>alert('Password Changed Successfully')</script>");
          }

          else
          {
              ClientScript.RegisterStartupScript(this.GetType(), "ErrorMsg", "<script>alert('Old Password Does Not Match with Records.')</script>");
          }
      }
  }

My stored procedure is:-

SQL

ALTER proc [dbo].[passwrdchange]
@ID bigint,
@oldpass varchar(MAX),
@newpass varchar(MAX),
@Out char output
As
Begin
Set @Out='F'

	if(Select Password from User_Information where ID=@ID)=@oldpass
		Begin
			Update User_Information Set Password=@newpass where ID=@ID
			Set @Out='T'
		End
	
End

And My Linq .cs file function for Calling stored procedure is:-

C#

private void UpdateUser_Information(User_Information obj)
	{
		this.passwrdchange(((System.Nullable<long>)(obj.ID)), default(string), default(string),ref default(System.Nullable<char>));
	}

But this is giving me an error

A ref or out argument must be an assignable variable

Please HELP!!

Posted 6-Feb-16 16:34pm

Deepak Kanswal Sharma

Updated 6-Feb-16 17:09pm

PIEBALDconsult

v2

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Comments

PIEBALDconsult 6-Feb-16 23:10pm

I suspect the problem is:

ref default(System.Nullable<char>)

Deepak Kanswal Sharma 6-Feb-16 23:24pm

So I should Replace it with char?

Sergey Alexandrovich Kryukov 6-Feb-16 23:11pm

What part of this error message is unclear? It should be a variable, not read-only field, not constant, not immediate constant...
—SA

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Sergey Alexandrovich Kryukov · Accepted Answer · 2016-02-06T17:22:00

Please see my comment to the question. Is anything unclear?

The problem is here:

C#

this.passwrdchange((System.Nullable<long>)(obj.ID)), default(string), default(string), ref default(System.Nullable<char>);

Here, your ref parameter is not assignable variable. This is the constant defined by the type. You need to understand passing parameters by reference. The calling method is supposed to fill in some place in memory. There is no such thing in your call. This would compile:

C#

System.Nullable<char> someVariable = // some value, null or not
this.passwrdchange((System.Nullable<long>)(obj.ID)), default(string), default(string), ref someVariable);
// but now:
// this call suggests that you can use the value
// of someVariable after the call

You have to learn this:
ref (C# Reference)[^],
out (C# Reference)[^],
Reference (computer science) - Wikipedia, the free encyclopedia[^],
Passing Parameters (C# Programming Guide)[^].

—SA