connection string code help

I can't figure out what is wrong with this code. The error is
A field initializer cannot reference the non-static field, method, or property 'clsKitInfo.connectionstring'      
this code sits in a class file named clsKitInfo. The problem is this line
protected SqlConnection cn = new SqlConnection(connectionstring);

protected string connectionstring = System.Configuration.ConfigurationManager.ConnectionStrings["SQLConnect"].ConnectionString;
protected clsconnect cnstr = new clsconnect();
protected SqlConnection cn = new SqlConnection(connectionstring);

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