Display only one Teacher Id on Teachers Column in DatagridView

Question

I am doing a application for a school using C# and database with SQL Server Management Studio and in one of the forms I want that when the teacher logged in only view the records from his, in order to hide the records from another teachers, so in the part of the code when I display all the teachers in datagridview I want to filter the "ProfessorId", column teacher id referent, to the id of the teacher that logged in while the application is running.

I am using my table for show classes from each teacher (ProfessoresTurmas), the column contain:

• Id Primary Key
• ProfessorId(Teacher's Id) Foreign Key from Teachers Table
• CursoId(Teacher's Course) Foreign Key from Courses Table
• TurmaId(Teacher's Class) Foreign Key from Classes Table

Image of the records of the table

Image of the table's design

Query working in sql server management studio

Thats the code that worked but only with the id that I wrote in the code, "Pr1" is one of the ids from the table but I want to detect automatically what's the teacher's id that is logged in:

private void DisplayTeachers()
        {
            Con.Open();
            string Query = "Select * from ProfessorTurmas where ProfessorId = 'Pr1'";
            SqlDataAdapter sda = new SqlDataAdapter(Query, Con);
            SqlCommandBuilder Builder = new SqlCommandBuilder(sda);
            var ds = new DataSet();
            sda.Fill(ds);
            DataGridView_student.DataSource = ds.Tables[0];
            Con.Close();
        }

Thats the code that I tried to wrote instead of 'Pr1' with UserCache.IdUser, thats the teacher's id logged in while the application is running:

private void DisplayTeachers()
        {
            Con.Open();
            string Query = "Select * from ProfessorTurmas where ProfessorId = " + UserCache.IdUser;
            SqlDataAdapter sda = new SqlDataAdapter(Query, Con);
            SqlCommandBuilder Builder = new SqlCommandBuilder(sda);
            var ds = new DataSet();
            sda.Fill(ds);
            DataGridView_student.DataSource = ds.Tables[0];
            Con.Close();
        }

But shows me this error:

System.Data.SqlClient.SqlException: 'Invalid column name 'Pr1'.'

In this line:

sda.Fill(ds);